Aqua Plumb, 1120, Radiator Valve Spud Wrench, Fits 1/2" to 2" Radiators, 6 Sizes. Aqua Plumb's Radiator Valve Spud Wrench is designed for making radiator valve repairs and can be used on 1/2" to 2" radiator valves. A radiator valve body is connected to the radiator by a spud. In order to remove the radiator valve a spud wrench such as this is required to loosen the spud. A spud wrench has grooves running down the side which grip a pair of nubs on the interior of the spud as the wrench is inserted into it, tightly securing it. It is a heavy duty tool and made from zinc.