A fin (originally called a skeg) is a strut located at the rear of the surfboard. The skeg was introduced in 1935 by Tom Blake. A surf board fin improves the board's fundamental directional stability, giving easier control of its direction by varying the surfer's weight distribution on the board. The skeg preceded the modern surfboard fin, a smaller, more hydrodynamically efficient version, which was developed in the late 1960s by George Greenough.