Shunt-ahead signals are used exclusively for shunting. They are generally fixed close to the ground and are either represented by a small arm or disc. The arm is held in the horizontal position to indicate a stop (with a red or white light at night) and moved 45° (with a green light at night) to indicate a proceed signal. The disc is white with a red stripe and the same positions are used for stop and proceed as with the arm. Proceed indications only apply insomuch as the line is clear.