A Carpenter's Work Sample

Almost.
A carpenter's-to-be work sample - one of the most useful things young apprentices used to make in their first year of apprenticeship.
This one is some 25 years old and the best bottle opener one can think of. 
I was told it takes quite a bit of accuracy to make it work just right and that it looks much more simple than it is to make it.

I don't know about that. But I know besides opening bottles you can use it for self-defense in case too many bottles had been opened.

19:20; 6°C