- Edited
Taz IMO (1) is an especially neat idea though I don't quite see how it would work in practice. If Keyholder A had both Key 1 and the change key what's to stop him/her using the change key so the lock would accept Key 1? Or have I missed something?
Surely Keyholder A should only have the change key and the Key 1 to open should only be held by Keyholder B?