HeadThe top corner of the sail, pulled up by the halyard.
TackThe lower front corner, fixed at the foot of the mast.
ClewThe lower back corner, where the outhaul or sheet pulls.
LuffThe front edge of the sail, along the mast.
FootThe bottom edge of the sail, along the boom.
LeechThe back edge of the sail, free of any spar.
TelltalesLight ribbons that show how the wind is flowing over the sail.
Shape and reefing: 6 5
RoachExtra cloth outside a straight line from head to clew. It adds sail area.
BattenStiff strips in pockets that support the roach. They keep the leech from fluttering.
Reef pointsA line of reinforced holes used to tie in a reef. That makes the sail smaller in strong wind.
Reef cringleA reinforced ring at the end of a reef line. It becomes the new tack or clew when reefed.
CunninghamA hole above the tack. Pulling it down tightens the luff to flatten the sail.
How this list was compiled: Read 2026-09-26. (1) Wikipedia, Sail components, https://en.wikipedia.org/wiki/Sail_components : head, tack, clew; luff, leech, foot; roach; battens; reef points and cringles; cunningham; telltales; bolt rope; leech line. (2) iNavX, Nautical terminology 101, parts of a sail, https://www.inavx.com/2023/07/14/nautical-terminology-101-parts-of-a-sail : head, tack, clew, luff, leech, foot; corners reinforced with rings, grommets or rope loops; battens stiffen the leech; roach adds area beyond the triangle; reef points and a clew reef cringle for reefing; telltales show the wind's flow; cunningham hole. (3) Lake St. Clair Sailing School, Sailboat parts and sailing terms, https://lakestclairsailingschool.com/sailing-resources/sailboat-parts-and-sailing-terms/ : head (top), tack (lower front), clew (lower back), luff (front edge), leech (back edge), foot (bottom edge). Licence: own work
The drawing: Drawn for this site by script, 2026-09-26. Own work, nothing traced. Licence: own work
How it works
These are the parts of a sail on a mainsail, the sail behind the mast. Every triangular sail has the same three corners and three edges; start with those and the telltales.
Read the full guide
Corners and edges
The top corner is the head, the lower front corner the tack and the lower back corner the clew. The luff runs up the mast, the foot along the boom, and the leech is the free edge at the back.
Shape
The roach is extra cloth beyond a straight line from head to clew. Battens in pockets hold it out and stop the leech fluttering. Telltales, light ribbons, show how the wind is flowing over the sail.
Reefing
To make the sail smaller in strong wind, it is lowered to the row of reef points and tied down. The cringle at each end becomes the new tack and clew. The cunningham, above the tack, tightens the luff.
A way to remember the corners: the head is at the top, and the tack and clew are both at the bottom, the tack nearest the bow.
Questions and answers
What are the three corners of a sail called?
The head at the top, the tack at the lower front corner and the clew at the lower back corner. Each is reinforced, because the corners carry most of the load.
What is the difference between the luff and the leech?
The luff is the front edge, attached to the mast or forestay. The back edge, the leech, is free, so battens are used to stop it fluttering.
What are telltales on a sail?
Short ribbons or yarns on the sail that show how the wind is flowing over it, on the luff, the body and the leech. Traditionally red ones go on the port side and green on the starboard.