Instead of faffing around with Layers, it would sometimes be handy to quickly be able to lock objects at multiple levels, so that when you want to unlock a specific object on a specific layer, it doesn't unlock every layer.

For example if you have 3 objects overlaying each other you could lock the lowest object by holding 'Ctrl' and tapping 'L' 3 times, twice for the second layer, etc.

To unlock, 'Ctrl' + 'Shift' + 'L', tapping L as many times as required depending on the layer.