Swivellink Stand Lock Plates attach to the end of the 3.0" (Imperial) or 80mm (Metric) square stand base extrusion end tapped holes. The 1.5" (Imperial) or 40mm (Metric) square adjustable stand extrusion is oriented to fit inside to 3.0"/80mm Square Extrusion. Included with this plate is the handle kit to lock the adjusting extrusion and easily set the height, as well as the mounting hardware to the tapped holes in the 3"/80mm square extrusion.