Installing New Sash Locks | Step by Step Instructions

August 13, 2017

Installing new sash locks on your old windows sounds like a simple task but there are a few things you need to be aware of. Will the new sash locks mount in the same position? Do the sashes fully close and align properly? How can you repair damaged screw holes so your new sash locks will be safe and secure? Let’s take a look!

Inspecting Your Existing Sash Locks

Before you remove the old sash locks you should inspect them for functionality. Standard sash locks consist of two main components, a hook and a latch. The hook portion of the sash lock is mounted on the top side of the upper sash meeting rail. The latch portion of the lock mounts on the top side of the lower sash meeting rail. When you engage the latch into the hook it should pull the upper and lower sash meeting rails together. This ensures a positive seal. You can confirm this by looking down from above as you engage the latch. You may need a step-stool to gain the proper vantage point. If they pull together the location of the latch is just fine, otherwise you may need to adjust the mounting location when installing new sash locks.

Repairing Stripped Holes

If the existing holes are stripped out, you have 2 options for overcoming this dilemma. You can repair the holes or relocate the latch to left or right and drill new holes in the sash. Simply offset the new latch about a ¼” off center. This will allow you to fasten the new latch to solid, undamaged wood, while no one will notice that that the latch is not perfectly centered.

The second option is to repair the existing screw holes. Use a ¼” drill bit to enlarge the existing screw holes. Place a few drops of wood glue in the holes then gently tap a ¼” wooden dowel into each hole. Once the glue cures, you can use a hand saw to cut the dowels flush with the sash. Then drill a small pilot hole in the center of each dowel.

Installing New Sash Locks

The first step is installing the hook. Use a tape measure to locate the center of the upper sash. Use a pencil to mark the centerline on the topside of the upper meeting rail. Place the center of the hook on the mark. Be sure the front face of the hook is about 1/8” back from the edge of the meeting rail to ensure that the lower sash will not come in contact with the hook when the sash is raised. Use the pencil or a scratch awl to mark the holes, then drill a small pilot hole on the mark. Finally, screw the hook in place using the screws that came with your new lock.

The next step is to partially open the latch. It should be open just enough so that the tip of the latch would start to engage with the hook as you begin to close it. Place the tip of the latch just inside the hook and align it on the same centerline as the hook. Once again, mark the 2 holes with a pencil or awl then drill 2 small pilot holes. In both cases the pilot holes need only be about 1/16” diameter, their primary purpose is alignment of the latch.


Meeting Rail Alignment

If both sashes are in the fully closed position and they meeting rails are not aligned vertically, you may need to shim the hook. Place a small wood shim under the hook to make up the difference.

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Need help installing new sash locks on your old double hung windows? Contact our support team at (815)-634-8922.