I have designed and used many different styles of rudder stocks, rudder head shapes, and rudder lock downs, over the years, and these are as simple as I could make in our work shop using nylon turned down and shaped for most of the components with a threaded both ends, stainless steel rod as the "pull up/ push down". It was simple, works faultlessly, is strong, and most of all it is easily and quickly manufactured in house on a good cost basis.