BOAT TRAILER DISC BRAKE FREE BACKING REVERSE LOCK OUT SOLENOID VALVENormally Open Free Backing Electric Solenoid Valve. Commonly found on boat trailers, the solenoid is required if using disc brakes with a surge actuator to prevent locking of the brakes while reversing. This Normally Open Reverse Solenoid operates on a 12 volt capacity and installs with two wires. One wire (either one) connects to tow vehicle reverse lights. One wire (either one) connects to ground. This valve is rated to 800 p. s. i. The solenoid is