Odell latch keys were most often used for communal doors to provide a level of security at a time when proper locks were much more expensive and the keys were much larger, making them hard to carry around.

While I knew these were used in Glasgow, I've never found one of their distinctive keyhole plates before. The Odell Night Latches, which these keys fitted into, are almost impossible to find.

I came across this unusual upside down T-shaped keyhole on the door of a Victorian townhouse in Glasgow today. It's for an Odell Night Latch Key, of the type shown on the right. Patented in 1792, they came in a wide variety of different shapes and you put them through the cross bar of the T and then lifted them up. They'd only open the latch if their shape fitted the inverse shape of the mechanism in the lock itself, which sat on the other side of the door.

Cont./