I had a really old shower head that need replacement for years! It took it off on occasion to clean it and some how either threw a part away or ??? I was able to just pull it from the arm--the arm has sort of like a ball shape and the head sort of snapped in!! I threw the head away and can't find another one that will hook up to the arm--it has no threads!!!!!!!!! I was clueless to this terminolgy until two days ago so please be patient with me!! so now the water shoots straight out of the arm and could knock you down the pressure is so strong!! is there something that goes on the arm to connect the head that requires no real effort? I am in a pretty old building!!