Panel Clamp

Bowed panels can be a thing of the past. This Veritas® product is the most effective panel clamp available. It is easy to use, tightens by hand, and is stackable for production work. Best of all, you can make double clamp bars of any length to suit your own needs. 
The specially serrated posts grip the bars, keeping a panel flat under any pressure load without allowing the bars to lift. Bars can be made by drilling 3/4" diameter holes in straight stock. 2 x 2s are fine, but 2 x 4s let you stack panels, since there is room for the top of one post and the bottom of another in the same hole. Adjustable O-rings on the posts let you clamp anything from 5/8" to 2" thick without any shimming; the clamp pads can be set dead center on the stock. The secret to the system is the balanced tension exerted on the bars. The greater the pressure, the more rigid the bars become. The screw has 5" of travel. 
The panel clamp set, with one head and one tail, does not include the wood.