To operate, insert the materials you wish to clamp together between the two red parts, slide the moveable part of the clamp up the rail until it won't move any further and then tighten the blue handle. If the clamp slips during tightening, unscrew the handle all the way and slide the moveable part up even more, then try again. You may also need to hold the moveable part in position until the handle is tight enough to hold itself.