BLUEMOMENT

Taken from a tip by our Pete Cooper & adapted for the boat:
When using a spanner in a confined space (or just about anywhere on the boat), tie a piece of string through the ring end if you want it to remain in your toolbox, and not over the side or in the bilge.

PS they collect / stash hammers you know.... nothings safe.

I use a loop of string, well a shoelace actually, which I loop through the spanner or whatever, then round my wrist. I also have one of these sprung clips that you find on the drawstrings of jackets which I slide up to stop it falling off my wrist. Saves dropping tools from the top of the mast when you're up there fixing things.