Our rudder kits, like most kayak rudders, come with a black plastic vee-block. It holds the rudder in the centered position when raised on-deck and locks the footbraces. Several of our customers have cut a wooden vee-block to replace the stock plastic part; it's quite an elegant touch. To make a wooden vee-block start with a scrap piece of pretty wood such as mahogany, teak, or even burled maple. Cut the rough shape with a coping saw, saber saw, or band saw, then sand the block smooth and epoxy it to your aft deck.
