Product details:

Horizontal dog clamp features automatic adjusting capability with vertical hold down clamping pressure. This is a dog clamp and is used with dog tables. Fits 3/4" (19mm) dog holes. 20mm dog holes are available. One hand clamp operation with strong clamping pressure. Has a .5" post and can be raised above the Table 5.5" for clamping above the surface. Simply position the clamp against the material and engage with one hand.