This photo shows a reefed sail using a slab reefing system. On this boat the reefing line runs through the cringle at the sail’s luff rather than using a horn. Note also that the position of the aft turning block on the boom is a little back from the cringle when the sail is reefed. This helps keep the sail taut for better trimming when reefed.
This mainsail has the second reef in. If you look carefully at the leach of the sail where it lies against the boom, you can see the cringle of the first (lower) reef point.
Depending on conditions, on a boat with two reef points and a double-line system, you can reef the mainsail in stages from the first to the second reefs - or go all at once to the second reef if needed.
Note also that this boat has lazy jacks in place that help hold the lowered part of the sail on the boom. No additional securing may be needed. But without lazy jacks, the bottom of the sail can blow about and get in the way. Go to the next page to see how to secure it.