My shower needed descaling and to do that I needed to remove the thermostatic valve cartridge so that it could be soaked in vinegar. It needed a 30mm spanner to loosen it so I made one from a strip of mild steel. As I was not planning to use it much I did not bother hardening it.
Workshopshed: It's hard in London
Someone commented on twitter it looks like an ancient sword, I don't know about that, more MadMax in my opinion.