The two-piece rudder, with a central pivot, has both an uphaul and downhaul.
In normal sailing the rudder weight will keep it below the water.
In shallow areas the uphaul can be applied to ensure the rudder does not drag on the bottom.
In deeper areas the downhaul can be applied to reduce the amount of float and keep the rudder vertical.
The downhaul is elasticated so that hidden shallow areas do not cause damage to the rudder or boat.