US Patent 7438098 Worktable that is extendible in two steps

A worktable includes two first rails arranged in parallel on a base, two guide rods movable along the first rails in a first direction and a second direction reversed to the first direction, two second rails respectively slidably coupled to the guide rods, a sliding plate fixedly mounted on the second rails, and a positioning device for locking the sliding plate to stop the sliding plate from movement relative to the base.