Trimax TMC10 The TMC10 features a Zinc alloy and a protective rubber bumper that prevents noisy rattling and abrasion to ensure your finish is not marked. Provides additional security for your camper, boat or trailer by securing the coupler on your trailer tongue. Also secures trailer door latches, cargo boxes and other types of doors. Features patented 1/4 turn technology that cannot be false locked. Provides dual force protection when used with the UMAX100 (sold separately). Features teeth inside the lock so the lock will not fall apart if cut. A coupler is the forward most part of a trailer tongue that envelopes and secures to the tow vehicle hitch ball. The lever on the coupler both allows the ball to be received into the coupler and prevents the ball from being removed. Accordingly, a coupler lever lock prevents the lever from moving into the open position. For maximum security when a trailer, boat or RV is hooked up to a vehicle, a coupler lever lock should be combined with an unattended trailer lock such as the UMAX100 or UMAX50. TRIMAX makes the world's toughest locks. Through value added engineering design, TRIMAX is committed to product innovation that holds up to the highest quality standards. TRIMAX provides maximum security for marine, trailer and tow, RV, performance truck, power sports and bicycle applications. Tested. Tough. TRIMAX..