If the lock has a round screw in cylinder, the measurements are in inches. The 2 most popular sizes are 31/32 inch and 1 & 1/8 inch, there are 2 other sizes which are rarely used. You can see there is not much difference in the sizes, so you need to be accurate.
These dead latch locks can directly replace the existing hook bolt lock. Take great care to measure the correct back set. This measurement is from the front of the faceplate to the centre of the cylinder. By fitting an exact replacement, you can use the existing key cylinder, and thumb turn.
If you prefer you may fit a handle or paddle handle to the inside for easier exit.
The lock release (electric strike) should be ANSI fitting. For single doors use 25mm extension lip, for double doors the lip extension is not required..
- Use a FLAT faceplate for lock and strike
- Use a RADIUS faceplate lfor ock and strike