Well, if it's not apparent from my handle, I'm a locksmith by trade.In the UK. I mentioned in another thread about unique tools I have and use and continue to buy

This thread is going to be an accumulation of those weird and wonderful tools and my edc and set ups. (mods, please move if I've put in the wrong sub)
I posted a one piece tool that's used for removing circlips on euro cylinders. Thought I'd kick the thread off with this guy as I was just using it a few moments ago. Known as a 'Key Shoe' These are purpose built by locksmiths and are a general 'homebrew' item. You make them by bending steel into a 'U' shape and drilling a hole to take a 'pin' key or like this one tapering a bolt to hold a 'pipe' key. It's used when making keys, either by hand or machine and then you'd dress them on with a file, to round the bit over etc also handy for general fettling of keys. There is a company that makes a purpose made key hoarse. I'll see if I can find a link for one or a photograph. These home made ones work for my needs and what I use them for.