How do I Fit a Sash Lock to an Internal Door?

Written by mark morris
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How do I Fit a Sash Lock to an Internal Door?
Use a jigsaw to cut out the door casing to fit around the lock keeper. (fretsaw image by Aleksandr Ugorenkov from

Fitting a window sash lock to a door can provide additional security to support the striker bolt latch by reinforcing the top or bottom of the door. A sash lock is a sturdy, flush mount latch typically mounted with short, brass hardware screws. For door installation, it is best to use a longer, coarse-thread steel screw to firmly anchor it to the door. Using one sash lock at top and one at bottom will more than double the security provided by stabilising the door to protect from impact.

Skill level:

Things you need

  • Sash locks
  • Pencil
  • Pry bar
  • Locking pliers
  • Clamp
  • Jigsaw
  • Sandpaper
  • Finish nails
  • Drill
  • Pilot bit
  • 1 inch screws

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  1. 1

    Position the sash lock on the door so that the latch mechanism is on the face of the door and the latch keeper is on the knob-side door casing---the flat trim that runs vertically between the door jamb and wall. Mark the outline of the lock on the door and casing. Position a second latch if desired and mark the outline on the casing.

  2. 2

    Pry the casing from the wall with a flat pry bar. Pull the nails through the back of the casing with locking pliers to preserve the face. Lay the casing on a sturdy work surface. Attach it with a C-clamp with one of the marked areas hanging over empty space.

  3. 3

    Cut the marked outline along the edge of the casing away with a fine-tooth blade in a jigsaw. Sand the edge smooth with 150-grit sandpaper to smooth any splinters. Reset the casing to cut the second outline and sand it smooth.

  4. 4

    Realign the casing with the door jamb and nail it to the jamb's edge with a finish nail every 10 to 12 inches.

  5. 5

    Reposition the locks on the door and mark the screw holes of the mechanism on the face of the door and the latch-keeper holes on the edge of the door jamb. Drill pilot holes in each marked spot with a 1/8-inch bit to a depth of 1 inch.

  6. 6

    Drive one 1-inch wood screw through each hole in the sash lock, two in the door and two in jamb, with a cordless screw. Close the door and test the latches for proper operation. Loosen the screws and realign the latch pieces if needed.

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