How To Install A Door Lock | The One Step Most People Forget

You probably think installing a door lock is a 10-minute job. Grab a screwdriver, take off the old knob, screw in the new one. But that’s when the door won’t close. The latch catches on the strike plate, or the deadbolt grinds. Suddenly a quick swap turns into an afternoon with the door half-open, wondering where the tape measure went.

The good news is that one detail — the direction the latch faces — determines whether your new lock works on the first try. This article walks through the full process, including the step most people skip: checking the door’s handedness and getting that bevel right. You’ll also learn how to avoid the common mistakes that turn a simple install into a security risk.

Why Latch Direction Makes or Breaks the Install

The latch on a standard lockset has a beveled edge — one side is angled, the other is flat. If the bevel faces the wrong way, the latch won’t slide into the strike plate as the door closes. Instead it’ll smack into the plate and refuse to retract fully.

The rule is simple: the beveled side should face the direction the door closes. For a door that opens into a room, that means the bevel points toward the door jamb when viewed from the inside. For an out-swinging door, it’s the opposite.

This also ties into whether the door is left-handed or right-handed — a label determined by which side the hinges are on and which way the door swings. Installing a lock intended for a left-hand door on a right-hand door will give you that same misalignment headache.

Skipping this check is one of the most common mistakes in the fact doc, right behind incorrect measurements. Getting the handedness and bevel right before drilling saves you from having to flip the entire mechanism later.

Why Measuring Once Saves You an Hour

Most people grab a lock off the shelf and assume it’ll fit. That assumption is the root of many installation problems. The issue isn’t just whether the lock is the right type — it’s whether the holes in your door line up with the lock’s backset and crossbore. Here are the mistakes that trip up DIYers most often.

• Skipping measurements first: Without measuring the door’s thickness and the existing hole positions, you risk drilling in the wrong spot, leaving the latch too high, too low, or angled.
• Inaccurate measurements: Even a millimeter off when marking the latch bore or deadbolt hole can throw the whole mechanism out of alignment, making the lock feel loose or bind.
• Choosing the wrong lock type: A lock rated for a standard 1⅜-inch door won’t work on a 1¾-inch fire door. Check the manufacturer’s specs for door thickness and backset compatibility.
• Improper screw fastening: Using screws that are too short or too long can compromise security. The strike plate and latch need full-depth engagement with the door frame.
• Over-tightening: Cranking screws down with a drill can strip the threads or crack the lock housing. Hand-tighten with a screwdriver until snug, then add a quarter turn.

Putting a tape measure and a pencil in your tool kit before you start is the cheapest insurance against a botched install. Measure twice, drill once.

The Strike Plate Problem

Even if the latch goes in perfectly, a misaligned strike plate can undo all that work. The strike plate is the metal piece screwed into the door jamb that receives the latch. If it’s off by even a quarter inch, the latch will bind against the edge, making the door hard to close, or worse, it won’t engage at all — leaving the door easily forced open.

The beveled side of the latch must face the door’s closing direction to engage properly with the strike plate — Home Depot’s guide covers latch beveled side direction in detail. Once the latch is correct, check the strike plate. A simple way to diagnose alignment is the “lipstick test”: apply red lipstick to the edge of the latch, close the door, and see where the color transfers onto the strike plate. That shows you exactly where to file or adjust the plate opening. It’s one method some professionals use to get a perfect fit without guessing.

If the strike plate is significantly off, you may need to enlarge the hole with a round file or reposition the entire plate. Never force the latch closed — that will damage the lock over time.

Each fix is straightforward once you know what you’re looking for. The lipstick test alone saves you from taking the whole lock apart just to check alignment.

Step-by-Step Installation Without the Headaches

With the most common pitfalls identified, here’s the actual order of work. You’ll need a drill with wood bits, a tape measure, screwdriver, chisel (for the strike plate mortise), and a pencil. If you’re installing a smart lock, make sure you have the manufacturer’s app ready.

1. Remove the old hardware. Unscrew the interior knob or lever, separate the two halves, and pull the latch and strike plate. Clean any paint or debris from the bore holes.
2. Insert the latch with the bevel facing the door’s closing direction. This is the step most people get wrong. Use the existing latch bore holes if they line up; if not, drill new ones at the correct backset (typically 2⅜ or 2¾ inches).
3. Secure the strike plate on the door jamb. Make sure the plate sits flush. If the mortise (the recessed area) is too shallow, chisel it deeper. Use the included screws — they’re sized for the latch mechanism.
4. Attach the interior and exterior components. For a smart lock, follow the manufacturer’s wiring and mounting instructions precisely. Most systems require you to attach the exterior keypad or touchscreen first, then snap on the interior unit.
5. Test the alignment. Close the door and check that the latch slides into the strike plate smoothly. If it sticks, repeat the lipstick test and adjust the plate.

Drilling placement is critical — the wrong location can force you to patch and repaint. Lowes covers drilling placement critical in their video guide, emphasizing that you should mark the center of each bore before picking up the drill.

Three Checks Before You Tighten Everything

Assuming the latch and strike plate are installed, three final checks separate a smooth operation from a frustrating one. First, confirm the door is level. If the door sags or the frame is twisted, no lock will line up perfectly. Use a carpenter’s level across the top and side edges of the door before you commit to the final screws.

Second, re-check the door’s handedness one more time. A door labeled left-hand but installed as right-hand can cause the latch to angle the wrong way. The fix is simple: flip the latch if you haven’t already, but catching it at this point beats having to remove the entire lock.

Third, test the latch’s engagement with the strike plate at both the open and closed positions. A misaligned strike plate can create security risks — Berger Hardware explains misaligned strike plate risks in more detail. If the latch barely catches, the door can be forced open with minimal effort. File the strike plate opening slightly or shim the plate to get a full, solid engagement.

A lock that clicks cleanly into place on the first try is a lock you can trust.

The Bottom Line

Installing a door lock is a DIY project that rewards patience. The make-or-break detail is the latch bevel direction — get that right, and the rest of the job is mostly line-up and tightening. Measuring the door first, leveling the frame, and using a lipstick test on the strike plate eliminate nearly every common mistake found in the installation guides.

If you’re unsure about your door’s handedness or the correct drill bit size for the backset, a local locksmith or home center associate can confirm the details before you start — saving you from buying the wrong lock or drilling into the wrong spot.