A reef knot is used to tie a line in a loop around something, like a square knot, but with the ability to quickly and easily release the knot. Reef knots are commonly used to tie up the baggy foot of a reefed mainsail around the boom.
A reef knot is very similar to a square knot. If you’re not sure you can tie a square knot correctly, check those steps first, then return to see what is different about a reef knot.
The main difference in a reef knot is that for the second overheard knot, you use a loop rather than the bitter end. Then to release the knot quickly, you jerk on the bitter end of that loop and pull the knot apart.
Step 1
Begin with a simple overhand knot. Note that at least one of the ends should be long enough to form a loop. (In this photo, the line end originating at the left side is intentionally longer for making the loop in the next step.)
