Designed for maintenance-free service life, Universal Locking Device works on almost all lubricated plug valves ranging from ½–8 in. in size with button top. Locking mechanism helps companies stay within compliance of CFR, 49 Transportation, Parts 186–199, 192.727 which states that when customer's service is discontinued, 1 of 3 steps must be followed to insure stoppage of gas flow; option 1 is installation of locking device or other means to prevent opening of shut-off valve.