The forces of the wind on the sails are matched by the forces underwater, mainly created by the centreboard. This resistance is called the centre of lateral resistance (C of LR) and it is a combination of the centreboard and hull shape. Without C of LR the boat will slide sideways, especially sailing upwind. The crew must ensure that the centreboard is set correctly for each point of sail. As the dinghy turns towards the wind (luffs up) and the mainsail is sheeted in, the board goes down. As the dinghy turns away from the wind (bears away) and the mainsail is sheeted out, the board comes up.