A sheet is a line (rope) used in sailing to control the angle and tension of a sail relative to the wind, enabling trimming for optimal performance. Attached to the lower corner (clew) of a sail or the boom, sheets allow sailors to "sheet in" (tighten) or "ease" (loosen) the sail.

Key Aspects of Sheets:
Purpose: They adjust the sail's angle to the wind, impacting speed and stability.

Naming Convention: Named after the sail they control (e.g., mainsheet for the mainsail, jib sheet for the jib).

Types: Usually made of strong, durable material like polyester or Dyneema.

Common Terms:
Sheet in/Trim: Pulling the line in to tighten the sail.

Ease/Ease out: Letting the line out to loosen the sail.

"Three sheets to the wind": A phrase originating from sailing, referring to a situation where all sheets are loose and the sails flap, causing the vessel to stagger or lurch.

Sheets are essential for managing sail power and differ from halyards, which are used to raise sails.