I need help in finding the fitting (Unsure of name) that is at the end of a hot water baseboard, not the bleed valve, but the other end of the radiator. It is like a plug I guess. This part was broken off, but says Keeney duo valve on it. It appears to be the same size as a typical bleed valve, but I don't know what that size is or what the name of this type of part is.