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A smart lock will fit only when its mechanical requirements match your door and existing deadbolt. Before buying or drilling, confirm that you have the lock format the product supports, measure the door thickness and bore preparation, and check the strike-plate clearance against that model’s current template.
The replacement examples documented by Aqara, eufy, TP-Link and SimpliSafe are intended for common single-cylinder deadbolts: a key cylinder outside and a thumbturn inside. Other door preparations may work with some products, but they are not automatically compatible.
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Start by identifying the lock you already have
Stand on the secure side of the door and inspect the deadbolt. A single-cylinder deadbolt has a keyed cylinder on the exterior and a thumbturn on the interior. Aqara describes its U100 as a replacement for this format, and SimpliSafe specifies the same arrangement for its cited Smart Lock. Those statements apply to the named products, not to every smart lock.
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TP-Link states the basic prerequisite for its Tapo DL100/DLW10 this way: “Your existing lock should be a single-cylinder deadbolt and meet the requirements for the following dimensions.” The wording matters: the lock format and the dimensions must both qualify. A single-cylinder deadbolt alone does not prove that the replacement will fit.
Measure the door before choosing a model
Record the measurements below with the door closed, then compare every value with the selected lock’s current manual and paper template. A measurement that fits one model is not a universal smart-lock standard. Use one unit consistently, or convert carefully between millimeters and inches.
Door thickness
Measure from the interior face of the door to the exterior face, excluding weather stripping or decorative trim. Aqara’s U100 lists 35–55 mm for a wooden door. eufy’s compatibility guide also lists 35–55 mm. If your door is outside that range, stop and obtain model-specific confirmation before ordering. A thicker or thinner door may require a manufacturer-supplied spacer or a different lock, not an improvised washer.
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The cross-bore is the large round hole through the door face where the lock body sits. Measure the hole itself, not the outside diameter of a decorative escutcheon. Aqara specifies a 54 mm door hole for the U100. eufy lists a supported cross-bore range of 38–54 mm. Measure at several points if the hole appears irregular; a tapered or damaged opening can prevent the mounting plate from sitting square.
Edge-bore diameter
The edge bore is the smaller hole in the door edge that contains the latch or deadbolt. eufy lists 25 mm for its compatibility requirements. Other locks may use a different size, so use the chosen product’s template rather than enlarging the hole by assumption. Check that the edge-bore center is at the same height as the cross-bore center.
Backset
Measure from the door edge to the center of the cross-bore. The common values are 60 mm (2-3/8 inches) and 70 mm (2-3/4 inches), but Home Depot’s general guide does not establish that either value fits every smart lock. Aqara’s U100 and eufy’s cited requirements support 60 or 70 mm. TP-Link’s Tapo DL100/DLW10 instructions likewise describe those two positions and explain that the bolt must be adjusted for the longer backset.
| Requirement | Aqara U100 | eufy compatibility guide | TP-Link Tapo DL100/DLW10 |
|---|---|---|---|
| Existing lock format | Single-cylinder deadbolt | Check the model guide; requirements are for compatible deadbolt preparation | Single-cylinder deadbolt |
| Door thickness | 35–55 mm wooden door | 35–55 mm | See the current model instructions |
| Cross-bore | 54 mm | 38–54 mm | Check the supplied chart and template |
| Edge bore | Use the U100 installation requirements | 25 mm | Check the supplied chart and template |
| Backset | 60 or 70 mm | 60 or 70 mm | 60 or 70 mm; adjust the bolt for 70 mm |
The values in the table are product requirements, not industry-wide dimensions. Aqara notes that modifications may be necessary when a door has different dimensions. Do not treat that note as permission to drill: first determine whether the manufacturer provides an approved procedure for your exact door.
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How to measure accurately
Measure with the door open when you need to see the edge bore, then repeat the backset measurement from the door edge to the center of the face bore. Do not measure to the edge of the existing trim ring. If the old lock has an adjustable latch, extend it fully and identify which setting is installed. Photograph the ruler beside each measurement so a manufacturer or locksmith can verify what you recorded.
Check the frame and surrounding clearance
A correctly sized lock can still fail if the bolt cannot enter the frame. With the door closed, inspect the opening behind the strike plate for wood, metal, insulation, or another obstruction. SimpliSafe lists an unobstructed strike plate and borehole among its prerequisites.
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Use the lock’s template to check the space around the cross-bore. Nearby levers, escutcheons, storm-door hardware, security bars, or thick trim can prevent the interior motor housing from sitting flat. Measure the clearance with the door both open and closed; a frame can hide interference that is not visible from the room side.
Confirm that the strike plate is aligned with the bolt. A bolt that already rubs or requires you to lift the door is a poor candidate for a motorized lock until the underlying alignment problem is corrected. A smart motor is designed to turn a freely moving bolt, not to force a sagging door into position.
Check the depth as well as the width of the strike opening. The bolt face should enter the opening without contacting the top, bottom, or sides. If weather stripping pushes the door away from the jamb, that pressure can become more noticeable after installation.
Decide whether the product replaces or adapts your deadbolt
When comparing compatible models, establish which hardware you will receive:
- Complete replacement: the package supplies a new bolt, exterior assembly, interior mounting plate, and lock body. The old deadbolt is removed.
- Retrofit attachment: the product attaches to an existing lock or thumbturn. The original exterior cylinder and some of the original hardware remain.
Do not infer the installation method from a product photograph. Verify the exact model number, included parts, allowed deadbolt types, and any required adapters in the current instructions. Also check whether your nearby handle or trim leaves room for the supplied interior assembly.
A retrofit can preserve an existing exterior key cylinder, while a complete replacement changes more of the door preparation. Neither approach is automatically better. Choose the one whose published dimensions match your door and whose installation steps you can complete without unapproved alterations.
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Prepare without modifying the door prematurely
Gather a tape measure or ruler, a pencil, and the screwdriver specified by the product manual. Aqara lists a PH1 screwdriver for U100 installation. Keep the manufacturer’s paper template, all screws, spacers, adapter plates, and the old lock until the new unit has been tested.
A door-lock installation kit or boring guide can help when a manufacturer explicitly requires a new or enlarged hole. Home Depot presents that equipment as a conditional option, not a universal smart-lock requirement. Drilling in the wrong location can leave the door unusable and may remove material needed for the strike or mounting screws.
Do not substitute a longer screw because it appears stronger. A screw that reaches too far can contact the bolt, wiring, glass panel, or another part of the door. Use the lengths and locations shown in the model’s hardware diagram.
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- Write down the lock’s exact model and revision, then open its current installation guide.
- Photograph the existing exterior cylinder, interior thumbturn, bolt orientation, and strike plate before disassembly.
- Measure door thickness, cross-bore, edge bore, and backset. Record millimeters or inches consistently.
- Lay the supplied template over the door and compare its centerlines with your measurements.
- Check that the frame, strike, handle, and trim leave the clearance shown in the guide.
- Count the supplied screws, adapters, batteries, and cables before taking the old lock apart.
- If any value is outside the stated range or the template does not sit flat, pause and contact the manufacturer or a qualified locksmith.
Model-specific installation sequence
The following sequence reflects the broad order described in TP-Link’s instructions for the Tapo DL100/DLW10 V1, last updated October 10, 2026. It is an orientation guide, not a substitute for the instructions supplied with your lock. Screw lengths, cable routing, bolt orientation, and included hardware vary by model.
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Open the door so you cannot accidentally lock yourself out. Remove the interior thumbturn and mounting screws, then separate the interior and exterior assemblies. Remove the edge screws and slide out the old deadbolt. Keep the pieces together in case you need to restore the original lock. Do not discard the original strike plate or keys until setup and testing are complete.
2. Set the new bolt to the measured backset
Compare the door’s backset with the two positions supported by the Tapo models. Set the bolt to 60 mm or 70 mm as directed; the longer position requires the adjustment described in the Tapo guide. Ensure the word or arrow marking on the bolt faces the correct direction for your door. A reversed latch or bolt can make the motor bind.
If your selected lock has a different adjustment mechanism, follow its diagram instead of copying the Tapo procedure. The apparent position of a sliding latch is not a substitute for measuring the actual backset.
3. Insert and secure the bolt
Slide the new bolt into the edge bore with its faceplate flush against the door edge. Do not force it into a hole that is too small or offset. Install only the screws specified by the model and tighten them evenly so the bolt remains square. Operate the bolt by hand before attaching the motor; it should travel smoothly with the door open.
4. Fit the exterior assembly
Pass the exterior cylinder, cable, or spindle through the cross-bore as shown in the template. Keep the cable clear of the bolt and do not pinch it between the door and the mounting plate. Hold the exterior unit level while starting the interior screws. If the exterior piece rocks, remove it and check the bore and alignment rather than tightening harder.
5. Install the interior plate and lock body
Route the cable through the designated opening, attach the interior mounting plate, and secure the lock body with the supplied screws. Tighten until the assembly is stable; overtightening can distort the door skin or cause the thumbturn and motor to drag. Confirm that the interior thumbturn or manual override moves through its full travel before fitting any cover.
6. Complete the model’s setup procedure
Install batteries or connect the power source specified by the manual, then follow that model’s pairing, calibration, and user-code steps. Connectivity and ecosystem features differ by product and should be verified in the current documentation rather than assumed from another lock. Keep the door open during calibration unless the instructions explicitly require another position.
Test the lock before relying on it
Leave the door open for the first tests. Turn the interior thumbturn or run the lock’s manual operation and confirm that the bolt extends and retracts without scraping. Close the door gently and check that the bolt enters the strike without pressure. Test the outside key or emergency method, if the model provides one, before closing the door from the secure side.
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- The bolt should move fully in both directions.
- The interior assembly should remain firmly seated without rocking.
- The door should latch without lifting, pulling, or pushing it into alignment.
- The strike opening should not contact the bolt tip.
- Any calibration or setup routine should complete as the manufacturer describes.
- The manual override or emergency entry method should be usable if the model includes one.
If the lock works only when you push or pull the door, fix the door or strike alignment before enabling automatic locking. A motor should not be used to overcome a mechanically binding door. Repeat the open-door and closed-door tests after any adjustment.
Troubleshoot by symptom
| Symptom | Likely cause | Action |
|---|---|---|
| The interior unit will not sit flat | Door thickness, bore size, or nearby trim is outside the model’s allowance | Re-measure and compare with the exact template; do not add spacers or drill unless the guide approves them. |
| The bolt stops before reaching the strike | Wrong backset position, reversed bolt, or an obstructed or misaligned strike | Recheck the 60/70 mm setting where applicable, bolt orientation, and frame opening with the door open. |
| The motor strains or stalls | Binding from a tight installation or door/frame misalignment | Remove power as directed, operate the bolt manually, and correct alignment before repeating calibration. |
| The exterior and interior parts do not connect | Cable or spindle is routed incorrectly, or the package is for a different lock format | Compare every part with the model’s assembly diagram; stop if the existing lock is not the supported single-cylinder type. |
| Existing holes do not match | Different bore, thickness, or backset than the product permits | Do not enlarge the holes by guesswork. Ask the manufacturer whether an approved modification exists or have a locksmith assess the door. |
| The lock calibrates with the door open but not closed | Strike alignment, weather-strip pressure, or a door that shifts in the frame | Correct the mechanical alignment first, then repeat the manufacturer’s calibration procedure. |
Compare compatible models on the dimensions that matter
If more than one lock passes the compatibility check, compare the supported existing lock format and exact measurement ranges first. Then compare whether each product replaces the full deadbolt or attaches to the existing interior hardware, what modifications are allowed, which adapters and screws are included, and how much clearance the interior housing needs.
Only after the mechanical fit is established should you compare features, app ecosystems, or connectivity. Current capabilities must come from the exact manufacturer product page and manual; a feature listed for one revision or model does not establish that another version has it. Hardware cost, installation-service cost, and availability also change by seller and date, so check the current listing rather than relying on an old price.
A directly relevant accessory is a boring guide or door-lock installation kit, but it is appropriate only when the selected lock’s instructions call for a new or enlarged hole. A locksmith assessment may be the better expense for a nonstandard door because it avoids an irreversible mistake.
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The cited installation materials do not establish general compatibility for mortise locks, multi-point locks, glass doors, narrow-stile doors, or every retrofit design. These doors may use a different lock case, spindle position, or structural layout. Treat compatibility as unresolved until the chosen manufacturer confirms it in writing or in a model-specific guide.
For a rented home, confirm that replacing the deadbolt is permitted and retain the original hardware. For a fire-rated, security-rated, or unusually thick door, ask the door or lock manufacturer whether changing the hardware affects its rating. A locksmith can inspect the preparation without committing you to irreversible drilling.
When to stop and get help
Stop the installation if the door does not match the lock’s stated dimensions, the strike cannot be made unobstructed without removing structural material, or the interior housing conflicts with trim. Also stop if the instructions call for a part that is missing or if the lock binds after careful alignment.
Contact the lock manufacturer with the model number, door thickness, bore and backset measurements, and clear photographs. For a nonstandard door or any proposed hole modification, a qualified locksmith can verify the preparation and install the hardware without relying on assumptions from another model.
Bottom line for a safe purchase
Measure first, then buy only a lock whose current documentation explicitly accepts your existing deadbolt and dimensions. Single-cylinder deadbolts with 60 or 70 mm backsets are common targets in the cited products, but the cross-bore, edge bore, door thickness, clearance, and strike alignment still decide whether a particular model fits. Follow that model’s template and sequence, test it with the door open, and seek manufacturer or locksmith guidance before altering an unusual door.
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Frequently Asked Questions
What type of deadbolt is usually required?
The cited Aqara, SimpliSafe and TP-Link examples require or target a single-cylinder deadbolt: a key cylinder outside and a thumbturn inside. Confirm the exact model because this is not a universal requirement for every smart lock.
What backset should I have?
The common measurements are 60 mm (2-3/8 inches) and 70 mm (2-3/4 inches). Aqara U100, eufy’s cited guide and TP-Link’s Tapo DL100/DLW10 instructions support those positions, but you must verify the chosen model’s current chart.
Can I install a smart lock if my door hole is a different size?
Do not enlarge or relocate the hole by guesswork. Aqara notes that modifications may be necessary for different dimensions, while Home Depot treats a boring guide as a conditional tool. Obtain an approved procedure from the manufacturer or use a qualified locksmith.
Should the door be open during installation and testing?
Yes. Remove and install hardware with the door open, and perform the first manual, calibration and key or emergency-method tests before relying on the lock with the door closed.
Why does the motor strain after installation?
A reversed bolt, incorrect backset setting, tight mounting screws, an obstructed strike or door/frame misalignment can cause binding. Operate the bolt manually, correct the mechanical issue, and repeat calibration; do not let the motor force a misaligned door.
Will a smart lock fit a mortise, multipoint, glass or narrow-stile door?
The cited installation materials do not establish general compatibility for those preparations. Treat the fit as unresolved until the selected manufacturer confirms it for the exact model, or have a locksmith inspect the door.
What should I send the manufacturer when asking about fit?
Provide the exact model and revision, door thickness, cross-bore and edge-bore diameters, backset, photographs of both sides and the door edge, and a clear image of the strike and surrounding trim.
Do smart-lock prices or installation costs have a fixed standard?
No fixed amount applies across models or doors. Check the current hardware price and, if needed, obtain a local locksmith quote. A boring guide or installation kit is a conditional expense only when the selected instructions require door modification.
The Bottom Line
Check the existing lock format and every measurement before ordering. A single-cylinder deadbolt, compatible door thickness, bore sizes, backset, clear strike and free-moving bolt are all required for a reliable installation. Use the exact model’s template, avoid unapproved drilling, test with the door open, and call the manufacturer or a locksmith when the preparation is unusual.
Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
