The bar-mounting corkscrew is a fascinating tool that had multiple upgrades with many patents in its evolvement. A general description would say that the clamps hold the bottle in place and the helix, in one up and down motion, extracts the cork from the bottle. They are screwed or clamped to the counter. Most early mounted corkscrews were designed to open beer bottles with short corks. Modern ones are made for longer wine corks.