Wheel changing
I once hit on the idea of having the threaded portion of a spare wheel stud for my car welded to a short shaft .The idea was that when changing the wheel I could screw the new tool into the hub and slip the spare wheel into position along the shaft to allow the other studs to be fitted without my having to prop the wheel in position with my knee. I later opened the toolbag in my Audi to find that Audi had beaten me to it in carbon fibre! Drat.