In sailing

Sailing

Sailing is the propulsion of a vehicle and the control of its movement with large foils called sails. By changing the rigging, rudder, and sometimes the keel or centre board, a sailor manages the force of the wind on the sails in order to move the boat relative to its surrounding medium and...

, a sheet is a line (rope

Rope

A rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...

, cable

Cable

A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...

 or chain

Chain

A chain is a sequence of connected links.Chain may also refer to:Chain may refer to:* Necklace - a jewelry which is worn around the neck* Mail , a type of armor made of interlocking chain links...

) used to control the movable corner(s) (clews) of a sail

Sail

A sail is any type of surface intended to move a vessel, vehicle or rotor by being placed in a wind—in essence a propulsion wing. Sails are used in sailing.-History of sails:...

.

Fore-and-aft rigs

Fore-and-aft rig

Fore-and-aft rig

A fore-and-aft rig is a sailing rig consisting mainly of sails that are set along the line of the keel rather than perpendicular to it. Such sails are described as fore-and-aft rigged....

s comprise the vast majority of sailing vessels in use today, including effectively all dinghies

Dinghy

A dinghy is a type of small boat, often carried or towed for use as a ship's boat by a larger vessel. It is a loanword from either Bengali or Urdu. The term can also refer to small racing yachts or recreational open sailing boats. Utility dinghies are usually rowboats or have an outboard motor,...

 and yacht

Yacht

A yacht is a recreational boat or ship. The term originated from the Dutch Jacht meaning "hunt". It was originally defined as a light fast sailing vessel used by the Dutch navy to pursue pirates and other transgressors around and into the shallow waters of the Low Countries...

s. The sheet on a fore-and-aft sail controls the angle of the sail to the wind, and should be adjusted to keep the sail just filled. Most smaller boats use the Bermuda rig

Bermuda rig

The term Bermuda rig refers to a configuration of mast and rigging for a type of sailboat and is also known as a Marconi rig; this is the typical configuration for most modern sailboats...

, which has two or three sets of sheets:

• The mainsheet is attached to the boom
  Boom (sailing)
  In sailing, a boom is a spar , along the foot of a fore and aft rigged sail, that greatly improves control of the angle and shape of the sail. The primary action of the boom is to keep the foot of the sail flatter when the sail angle is away from the centerline of the boat. The boom also serves...
  
  , and is used to control the mainsail
  Mainsail
  A mainsail is a sail located behind the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast....
  
  . In a rig with no boom on the mainsail
  Mainsail
  A mainsail is a sail located behind the main mast of a sailing vessel.On a square rigged vessel, it is the lowest and largest sail on the main mast....
  
  , the mainsheet would attach directly to the mainsail clew. A mainsheet is a rope connected to the boom which allows a sailor to control the speed of a boat.
• The jib sheet attaches to the clew of the jib
  Jib
  A jib is a triangular staysail set ahead of the foremast of a sailing vessel. Its tack is fixed to the bowsprit, to the bow, or to the deck between the bowsprit and the foremost mast...
  
  , and controls it. The jib has a sheet on each side, only one of which (the leeward one) will be in use at one time.
• The spinnaker sheet attaches to the clew(s) of the spinnaker
  Spinnaker
  A spinnaker is a special type of sail that is designed specifically for sailing off the wind from a reaching course to a downwind, i.e. with the wind 90°–180° off the bow. The spinnaker fills with wind and balloons out in front of the boat when it is deployed, called flying. It is constructed of...
  
  , if carried. A symmetrical spinnaker has two sheets, an "active" one and a "lazy" one, in the same way as a jib, but they are attached to the sail's two separate clews. On boats larger than around thirty feet, the spinnaker will also be fitted with guy
  Guy (sailing)
  A guy is a term for a line attached to and intended to control the end of a spar on a sailboat. On a modern sloop-rigged sailboat with a symmetric spinnaker, the spinnaker pole is the spar most commonly controlled by one or more guys.There are two primary types of guys used to control a...
  
  s, which are similar to sheets but control the pole instead of the sail. On smaller boats the lazy sheet is used as a guy.

On the smallest boats, a sheet is often a simple rope, pulled by hand; on larger boats, usually on the mainsheet, it is often a system using several blocks

Block (sailing)

In sailing, a block is a single or multiple pulley. One or a number of sheaves are enclosed in an assembly between cheeks or chocks. In use a block is fixed to the end of a line, to a spar or to a surface...

 to provide mechanical advantage

Mechanical advantage

Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. Ideally, the device preserves the input power and simply trades off forces against movement to obtain a desired amplification in the output force...

. At one time, headsail sheets on yachts also involved blocks, but the disadvantages of having large amounts of line and loose blocks free to move all over the forward part of the vessel mean that such systems have been almost universally replaced with single-line sheets holding immense forces but controlled by powerful winch

Winch

A winch is a mechanical device that is used to pull in or let out or otherwise adjust the "tension" of a rope or wire rope . In its simplest form it consists of a spool and attached hand crank. In larger forms, winches stand at the heart of machines as diverse as tow trucks, steam shovels and...

es.

Square rig

Square rigged vessels are much less common, and are usually large ships. Nevertheless, they too have sheets on the movable corners of their square sails. Unlike fore-and-aft sheets, though, square-rig sheets do not control the angle of the sails (which is performed using braces

Braces (sailing)

The braces on a square-rigged ship are lines used to rotate the yards around the mast, to allow the ship to sail at different angles to the wind....

); instead, they are used to haul the corners of the sails from their stowed positions down towards the tip of the yard below. They are then not adjusted significantly while sailing until the sail is to be handed (put away) again.The lowest sails, Courses, are trimmed using the sheets as these sails are loose footed being secured to yards only at the head.

Three sheets to the wind

The term "three sheets to the wind," meaning "staggering drunk," refers to a ship whose sheets have come loose, causing the sails to flap uncontrolled and the ship to meander at the mercy of the elements. The TV show Three Sheets derives its name from the expression "Three sheets to the wind," from which it removes the latter part.