Backing a sail involves pushing a sail against the wind to create resistance. This action stops the forward movement of the boat or forces it backward. A sailor pushes the boom out to back the mainsail during a maneuver. This technique helps the boat turn through the wind in very light air. It is also a useful way to slow down quickly before reaching a dock. The pressure of the wind on the front of the sail acts as a brake. Using this method allows for precise control of the boat speed in tight spaces. Mastering this skill helps the crew handle the vessel safely in crowded harbors.