hornyaspie2 That silly so how to unlock it when it really needed?
Sorry I didn't explain change key locks well.
A change key lock usually has 7 numbers engraved on the front of it 1-7 or 0-6 depends on who makes them.
They could be bought with any number from 1 to 7 of different keys and a change key.
Assume we only have key No 1 and the change key.
To use the lock you insert the change key and turn it to position No 1. The lock will now work like a perfectly normal lock with key No 1. If you now use the change key again and turn the lock to any or the other 6 positions key No 1 will no longer work in this lock. As soon as you reset it to one key No 1 will work again.
The reason these sort of locks could be useful on a belt is that both parents can hold a key and the lock can only be opened by both of them together, first the change key then the unlocking key.
There may be reasons to have several people with permission to unlock the belt. It is perhaps possible that the wearer may be going to stay long term with another relative and the belt could be programmed to their key before departure.