How to Change Locks

July 2, 2026 · 9 min read

To learn how to change locks, first decide whether you need new hardware or only new keys; then fit a compatible lock and test it before closing the door. Keep the door open while you check that the key, latch, and deadbolt all work.

Choose Between Replacing a Lock and Rekeying It

Changing a lock can mean replacing the lock hardware or changing which key operates the existing hardware. Choose based on what you need to fix: replace the lock when parts are damaged, worn, or unsuitable for the door; consider rekeying when the lock works and you want it to accept a different key.

Replacement makes sense if the key sticks because the cylinder is damaged, the latch does not move reliably, or the hardware is loose or broken. It can also be the right choice when you want a different lock style or need to replace a lock after moving into a home. Check the door and existing hardware first so the replacement fits.

Rekeying changes the lock cylinder so the old key no longer operates it and a new key does. It may suit you when the lock is in good condition but you want to change who has access. If you are deciding how to rekey locks, remember that the process depends on the cylinder design; it is not the same as simply copying a key.

Before you start, make sure you own the property or have permission to work on the lock. If you rent, share an entrance, or are unsure who controls the hardware, check with the property owner or manager before changing it. For a lock that needs both a new key and repairs, replacing the hardware may be more appropriate than rekeying.

• Replace the lock — Choose this when the lock, latch, or cylinder is damaged, unreliable, or the wrong style for your needs. Replacement means removing the old hardware and fitting compatible hardware in its place.
• Rekey the existing lock — Consider this when the lock works properly and you want it to operate with a different key. The lock stays in place, but its cylinder must be compatible with the rekeying process.
• Repair or get help — If the door is sagging, the lock binds, or parts do not line up, a new lock alone may not solve the problem. Identify the cause before changing hardware, or ask a locksmith to inspect it.

Compare the Main Lock Options

The right choice depends on the condition of the lock, the door, and the kind of access change you need. Compare the options before buying hardware or taking the existing lock apart.

Gather the Tools and Check the Door First

Before you remove anything, read the new lock’s instructions and compare its parts with the hardware already on the door. A little measuring can prevent a trip back for a part that does not fit.

• Tools — Have a screwdriver that fits the existing screws, a tape measure, and a pencil for recording measurements. Keep the new lock instructions nearby and use the tools specified by the manufacturer.
• Replacement hardware — Check that the package includes the lock body or latch, strike plate, screws, and keys that the instructions call for. Do not assume every kit has identical parts.
• Door measurements — Measure the door thickness, the distance from the door edge to the center of the knob or deadbolt hole, and the size of the existing holes. Compare those measurements with the new lock’s requirements.
• A safe work setup — Work on a door you own or are authorized to maintain. Keep the door open during fitting and testing, and keep the old hardware together until you know the new lock works.

How to Change Locks: Step-by-Step

These steps cover a typical screw-mounted entry lock. Lock designs differ, so follow the instructions supplied with your hardware. If a part does not match the instructions or does not come apart with ordinary pressure, stop rather than forcing it.

1. Keep the door open and identify the hardware — Open the door and make sure it cannot swing shut while you work. Identify the knob or lever, deadbolt if present, latch, strike plate, and the screws that hold the hardware together.
2. Record the existing fit — Measure the door thickness and the lock’s position from the door edge. Compare the existing latch and hole sizes with the replacement instructions; confirm the new lock is made for those measurements.
3. Remove the inside hardware — Use the correctly sized screwdriver to remove the interior mounting screws. Support both sides of the lock as the screws come out so the outside piece does not drop or pull against the door.
4. Take out the latch — Remove the screws on the narrow edge of the door and slide the latch out. Note which way the angled side faces, then compare the old latch with the replacement before installing the new one.
5. Fit the replacement latch — Place the latch into the door edge in the orientation shown in the instructions. Fasten it without overtightening, then check that its face sits flat against the door and that the latch moves freely.
6. Install the lock body — Position the exterior and interior pieces through the door and connect them as directed. Start the screws by hand, then tighten them evenly; check that the handles and key cylinder are straight and not pinched.
7. Replace or align the strike plate — Fit the strike plate to the door frame using the supplied instructions and screws. With the door still open, turn the knob or key to confirm the latch or deadbolt extends and retracts without catching.
8. Test before closing the door — Test the key from both sides where the lock is designed for it, and operate the handle several times. Only close the door after the lock moves smoothly; then test it again while keeping another exit available.

Check the Fit Before You Rely on the New Lock

A lock can look installed correctly but still bind because the latch and strike plate do not line up. With the door open, operate the key and handle several times. The latch should move fully, the deadbolt should extend and retract, and the lock should not shift when you use it.

Next, close the door gently and test the handle and key without forcing them. If the key turns easily with the door open but becomes difficult when the door is closed, inspect the alignment between the latch or bolt and the strike plate. Do not keep applying force; it can damage the key or lock.

Check that screws are snug and the lock sits level against the door. Screws that are too tight can interfere with movement, while loose hardware can wobble. Follow the product instructions if they specify a particular adjustment or testing sequence.

• Key turns smoothly — Test the key with the door open first. If it catches or will not turn, stop and check the installation instructions rather than forcing it.
• Latch and deadbolt move fully — Operate the handle and key several times while the door is open. Confirm that each moving part extends and retracts without sticking.
• Bolt lines up with the frame — Close the door gently and check whether the bolt enters the strike plate cleanly. A scrape or bind can point to an alignment issue.

What Can Go Wrong When You Change a Lock?

If the new lock does not work as expected, do not force the key or handle. Reopen the door if possible, then check the part that is not moving and compare your installation with the lock instructions.

• The replacement does not fit the holes — The lock may require different door measurements or a different latch configuration. Stop before enlarging or modifying the door, and confirm the hardware requirements.
• The latch faces the wrong way — A reversed latch can prevent the door from closing or opening normally. Check its orientation against the instructions and correct it while the door is open.
• The key or handle binds — The lock may be misaligned, overtightened, or assembled incorrectly. Loosen and check the installation only as the instructions allow; do not force a stuck key.
• The door or frame is damaged — A loose frame, worn screw holes, or a door that shifts can keep the bolt from lining up. Hardware replacement may not address the underlying fit problem.

Know When to Call a Locksmith

Call a locksmith if the lock is damaged, the hardware does not match the door, the key or bolt remains stuck, or you cannot identify the right replacement. A locksmith can assess whether the situation calls for a repair, a new lock, or rekeying rather than having you force parts that do not fit.

Get help if the door will not stay open during the work, the lock is part of a shared or managed entrance, or you are unsure whether you have permission to change it. Do not try to open or defeat a lock on a door, home, or vehicle that you do not own or have authorization to service.

Locksmith Xpress is a mobile locksmith based in Gaithersburg and serving Montgomery County. We come to your home, car, or business; there is no storefront to visit. If you need our lock change & installation service, we can handle the work on site. You can also learn about our locksmith in Gaithersburg service area.

• The lock will not operate after installation — Stop using force if the key, latch, or deadbolt binds. A locksmith can inspect the lock and door alignment to determine what needs attention.
• The hardware is unfamiliar or incompatible — Some lock assemblies require specific parts or a different installation method. Ask a locksmith to identify the hardware before you alter the door.
• You need a mobile service visit — Locksmith Xpress provides mobile service in Gaithersburg and throughout Montgomery County. Use the contact page to get in touch.

After the Lock Works, Keep the Change Organized

Once the new lock passes the open-door and closed-door tests, keep the instructions and any spare parts in a place you can find later. Confirm which keys operate which doors, and make sure everyone who needs access has a working key. If you rekeyed the existing lock instead, label the new keys clearly and set aside old keys that no longer work.

Keep an eye on the lock during normal use. A new scrape, loose handle, stiff key, or bolt that no longer lines up can signal a fitting issue. Address it while the lock still operates rather than waiting until the door will not open or close.

For a door with unusual hardware, a damaged frame, or a lock that continues to bind, professional help can prevent more damage. Our lock change & installation service is mobile, so the work is done at your location.

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