Leech line

All UK Sailmakers sails come standard with a leech line that runs under the back edge of the mainsail. It can be tensioned to prevent the leech from fluttering. The standard arrangement is to have the line run from the top of the sail down to a cleat just above the clew. 

On boats with high booms, this is not a practical location for the leech line cleat.  A better solution is to upgrade to an “Over the Head Leech Line” where the adjustment for the leech line is at the tack of the mainsail. The leech line starts at the clew of the sail, runs up the leech, and then comes to a block at the head of the sail that turns it down the luff to the cleat just above the tack of the sail. This is a more expensive option, but a necessity on boats with high booms.

The standard location for a leech line cleat is just above the clew of a mainsail

Notice the block on the back of the headboard that turns the leech line so that it comes down the luff to a cleat above the tack. An over the head leech line is needed on boats with high booms and it is the only leech line set up that can be adjusted when the back of the boom is not over the boat.