For boat balance and speed, the shape of the headsail, jib/genoa, should be identical to the shape of the mainsail, which is influenced by wind speed and sea conditions. The headsail will be referred to as the jib in his blog. A twist occurs when the upper section of the jib falls off to the leeward side due to insufficient leech tension. The amount of twists in the jib should be about the same as the twist in the mainsail. "Jib Sheet," black stripes are running parallel to the deck on the sail, aid in determining the depth and position of the draught in the sail. Observe the amount of backwind in the mainsail to see if the jib is trimmed too tight and/or the draught is too far aft. The jib is over-trimmed and/or draughts too far forward in the sail if the backwind extends further back in the mainsail than typical, closing the slot and disturbing the flow of air between the mainsail and the jib. To counteract this, move the jib lead forward, causing the clew to pull lower, increasing leech strain and reducing twist.