Accuform STOPOUT Trailer Lock Glad Hand Lockout Deter unauthorized drive-off of trailers by blocking access to the emergency brake air line. Attach the glad hand lockout to the trailer (red) line connection and secure it with your choice of padlock to control access. The clam-style device measures 4″ (L) x 3″ (W) x 2″ (D). Made from durable plastic with a zinc-coated steel pin for the hinge. Fits standard-size valve.