Simply put, it keeps the sprit from flying upwards when under load generated by flying sails or anti torque line. The Trogear bowsprit is designed to be used in a horizontal position, same as for any other bowsprit. The loads generated by flying sails (Code 0, Asymmetric spinnakers, or other downwind sails) will create a force upwards. The bowsprit must be held securely in a horizontal position by a bobstay to prevent it from swinging up. WARNING: Never fully release the bobstay when under load. If it is accidentally released, it could lead to personal injury, boat and/or equipment damage, or the failure of the bowsprit itself.