The water supply line that comes out of the wall or floor has a handle and when turned one way or the other will open or close and turn on or off the water to that particular plumbing fixture. The plumbing pipe coming out could be one of several types and depending on which type of plumbing repair pipe will dictate the type of angle stop is being used. Copper pipe typically being 1/2″ if not sweated on will be a compression fit angle stop. Like the one to the right here, this large nut encompasses a washer inside and when slipped over the copper supply line, the washer will crimp around and seal itself onto the valve body, to then give you control over on/off and variable water pressure at the turn of the handle.

The angle stop on the left here is of a 1/2″ pipe threaded type and is common in any brass or galvanized pipe nipple application, theoretically both of these more used angle stops are of a mechanical based application that any person with 2 wrenches can put on or take off. The weekend DIY warrior need only one voice in their heads to reassure them they can DIY plumbing repair.