A lazy jack, or lazyjack, is a piece of nautical equipment that helps sailors control a fore-and-aft-rigged sail or a mainsail while reefing, furling, or securing it. This age-old system is a type of rigging, which, by connecting two or more points on the mast to two or more points on the boom, prevents the lowered sail from falling off the boom and onto the deck. Often referred to as self-flaking, this rigging usually reduces the number of crewmates required to secure the sail, thereby making it an important asset to many sailors. Using this method, a single sailor can usually handle this task alone.
The lazy jack system consists of a set of lines placed on both sides of the main sail. Top segments are attached at a high point on the mast and extend down to two or more line segments that are attached at different points along the boom. When the sailor furls the sail, the lazy jacks guide the sail down and capture it between these lines. A sail typically remains cleaner since the sail does not drop onto the deck and the sailors are not handling it as much as on a sailboat not equipped with lazy jacks.
Rigging with lazy jacks is the oldest self-flaking method and is still frequently used in modern times. A few systems, such as the Dutchman system, are modifications of the lazy jack system. One of the main differences between these two systems is that the lazy jack's lines rest on each side of the sail and the Dutchman's lines are on a single side and thread through holes in the sail.
Lazy jack designers typically need to customize the mounting points on booms and masts of sailboats. To have a properly working system, the lazy jacks usually need to be properly sized, installed, and adjusted. If the sail flakes unequally over the boom, the uneven weight can possibly damage a spreader and make the sail harder to store. Another problem with the lazy jack is that the lines often tangle when a person raises the sail.
Many boat owners rig their own lazy jacks or purchase after-market kits. Generally, companies sell kits for all sizes of sailboats, from dinghies to large yachts and cruisers. They usually design them for boats with full-battened mains as well as boats with standard sails. When purchasing a kit, a boat owner usually compares the line composition, which can vary from nylon rope to plastic-clad steel cable, and the types of hardware.