These Master Lock® Installed Bases help protect against accidental reengagement of a machine during maintenance or repair by prohibiting access to a switch or control when properly paired with the S2151 Removable Push Button and Rotary Switch Cover. It allows one removable cover to service multiple switches on the same panel. In addition, the horse-shoe shaped retrofit base allows use with raised nameplates and off-center installation to accommodate rotary switch knobs. Furthermore, the clear base provides visibility to nameplates and labels for added safety. Ideal for 1¼” (30.5mm) and 9/10” (22.5mm) diameter switches. It may also be incorporated into a comprehensive OSHA compliant lockout/tagout safety program.