Bar-Lok Quick-Acting Screw Clamps

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Definitely the strongest quick-acting screw clamp available. The patented grooved-bar design works smoothly and positively - just slide the bar forward to contact the workpiece, then turn clockwise to apply force. To unclamp, turn counterclockwise and slide the bar back. As strong as a standard screw clamp, but much faster.

[@esmute]

I have some very old clamps with this system. I've never seen anything like that.