Abstract: A cap (100) having threads (109) along a rim (107) of an opening (105) in an end of a body (101) screws on a faucet (300) having complementary threads (311) on which a packing nut can be installed. A cavity (103) inside the body (101) is capable of receiving and covering a valve stem (307) to prevent the unauthorized use of the faucet (300). A securing member, such as a screw (113) that passes through a hole (115) in the body (101), secures the cap (100) to the valve stem (307) to prevent removal of the cap (100) from the faucet (300).