What is a dropped snib? Is it one of the many ailments that torment us over-fifties?
Snib or holdback are the correct terms for the part of a lock that stops a door latching behind you as you pop out to the dustbin in your dressing gown. It’s often incorrectly called the latch; latch, however, is what a door is doing if it locks as it closes, without your having to take any action other than close the door.
On locks that don’t have much sophistication, as well as holding the latchbolt open, the snib can also lock the latchbolt closed even against the correct key.
A dropped snib is when the snib gets loose, and when the lock is fitted to the unlucky side of the door, and when as you slam the door and it latches shut, the snib falls down and locks you out.
So, which way would your snib be going if it fell downwards? Would it be falling towards inactive? Nice green tick! Or falling towards active? Nasty red cross! If, for example, you had a Yale rimlatch lock on the right-hand side of your door (looking at the door from the outside), then I’m afraid it doesn’t fail safe, it fails the vexatious way.
If you have a simple latch lock and it’s on troublesome side of the door, keep an eye out for the snib getting loose and floppy.
If you like finding things to worry about, I have one more for you. Is there a big gap between the door and the frame? It has been known for a latch lock to be snibbed to the locked state while the door is actually open, and then for the door to slam shut. The gap is big enough that the bevelled latch bolt can enter the bolthole, but it can’t then be got out again.