Single-line reefing is a method used to reduce the area of a sail on a sailing boat by pulling down a portion of the sail to make it smaller. This technique allows sailors to adjust the sail size quickly and efficiently, especially in strong winds, without needing to lower the entire sail. In single-line reefing, a single line is used to control the reefing process, making it easier for the sailor to manage the sail from the cockpit. This system typically involves a series of pulleys and hooks that help secure the reefed sail, ensuring it remains stable while sailing.