Only useful for clamping tongue and groove floors that are being face nailed. It is possible to clamp 8 to 10 boards at a time. Tremendous pressure can be applied to the boards. The clamps are always used in multiples; one clamp is useless. Spaced say every 4th or 5th joist, the clamp is driven onto the joist (range 35 mm to 65 mm thick) and with the ratchet action of the handle the clamp drives into a temporary bearer (100 x 50) and then to the boards.