Safety edges are mounted on the edge of the gate (front and back) and have a built in sensor that sends a signal to your gate opener to reverse or stop. An important safety device to add to your gate to prevent injuries, property damage, lawsuits and to conform to UL guidelines. You can hard wire the safety edge directly into the gate opener control board or use a receiver/transmitter to transmit the signal wirelessly. Remember, A Gate Can Never Be Too Safe®