What bone do you use when opening a door?

Usually when doing something like this or anything at all really, you use muscle and not bone. Bone is the structure for your body but your muscles do all the work. But the muscles you would use when opening a door also depend on the door you are opening, but I will assume you mean a standard rotate the door knob door. You use the muscles in your forearm to turn the knob and then you use your bicep to bring the door towards you. Hope this helped whatever you were doing.