Abstract: There is provided a system for locking skis of a snowmobile to the upper surface of a platform. The system includes a stationary shaft having a lower portion secured to the platform and an upper portion for supporting an adjustment nut and a crank handle that rotate about the upper portion. The upper portion of the stationary shaft has multistart or multilead threads at its outer surface. Also, a lock bar is situated below the adjustment nut so that it may be adjusted between a first position where the lock bar holds the skis against the platform and a second position where the lock bar releases the skis. In particular, the adjustment assembly changes its vertical position when rotated about the upper portion of the shaft and, thus, is capable of adjusting the vertical position of the lock bar as well.