Handwheel on top and interlocking teeth on two pivot plates providesimple, sure adjustment to work angle needed. Two sizes vary in heightto fit all applicable platforms as listed. Pivot range permits 140degrees,adjustment in increments of approximately 9 degrees,per tooth onmatching plates. Turning handle raises and lowers upper plate;stainless-steel guide pin keeps plates aligned. Groove in upper platecenters on rib in base to assure teeth engagement at every anglesetting.