Mid-reef with slab reefing, the boat lurches before you've set the leech cringle. To save time, a crewmember starts knotting the reef points along the folded belly of the sail. Why is this a mistake?

The reef points aren't load-bearing, so if they take the strain before the cringles are set they can tear the sail

Tying the reef points first is fine and actually holds the reef until the cringles are set

⛵ When & How to Reef the Mainsail

Reefing means reducing the mainsail's area so the boat carries less power in stronger wind. Recall from earlier cards that weather helm — the boat's urge to turn up into the wind — grows as the boat heels. When you're fighting the tiller, heeled past ~20°, and the boat feels overpowered rather than fast, that's the signal. The sailor's rule of thumb: the first time you wonder whether to reef, it's already time to reef. Reefing early is easy on flat-ish water; reefing late means wrestling a flogging sail in a building sea.

Read the signs together: sustained heel that won't ease when you dump the mainsheet, heavy weather helm, spray coming aboard, and wind in the high teens to low 20s (knots) for a typical cruising boat. As a very rough guide, many cruisers take a first reef around 18–20 knots and a second around 25, though the exact numbers depend on the boat and crew.

The classic method is slab (or 'jiffy') reefing, which folds down a slab of sail and ties it off:

Head close to the wind (or heave-to) to depower the sail, ease the mainsheet and boom vang, then: drop the halyard to the marked point, secure the luff reef cringle at the tack (over a horn or hook), haul the leech reef line to pull the new clew down to the boom, then re-tension the halyard. The loose belly of sail is tidied with the reef points, but never tie those first — they aren't load-bearing and can rip the sail if the cringles aren't set. In-mast (furling) reefing is simpler: ease the outhaul while rolling the sail into the mast, keeping light tension so it winds smoothly and doesn't jam.