These quick action clamps are by far amongst the most convenient, strong & accurate. These clamps have the quickest adjustment mechanism - simply lifting the Aluminium die-cast handle allows the sliding jaw to be moved anywhere on the rail 

The rail is made from special "K" section steel profiled to minimize flexing & bending. The steel rails have serrations that engage with a hardened steel insert in the moving jaw to eliminate slippage. Four hardened rollers in the moving head maintain a constant 90° angle under load, ensuring that the clamp heads remain parallel to each other & at right angles to the rail at all times. The clamp jaws are encased in non-marring, glue resistant polypropylene casing