Union 9094 13mm Mortice Latch Rebate Kit

How do I know which size rebate I need?

To determine the size of the rebate you require, simply measure the depth of the overlap between the two doors.

Will using a rebate kit invalidate the British standard on my door lock?

Yes, the use of a rebate kit will invalidate the British Standard BS3621 as the standard method of installation on which it is tested is not being used. It is therefore important that the end-user informs their insurance company that a BS3621 lock has been fitted with a rebate to allow the correct method of installation so it is noted on their policy.