Problem: you are out at work all day but need to let builders into your home. If you lend them a key it could be copied for nefarious purposes. Malachi McKenna of London has a clever solution: a single lock controlled by two different keys (patent application GB 2393479).
The lock looks normal, with a keyhole and a sliding bolt. But inside there are two separate sets of levers, shaped to be operated by two different keys. A mechanical slider hidden inside the lock moves the lever sets so that one or the other is positioned to receive a…
