Gate Keepers feature a U-Bolt that mounts to any round pipe between 1-3/8" to 2-3/8" in outer diameter. The Duck Bill design of the keeper forces the keeper into a receiving open position until it is engaged by a gate. When a gate opens into the keeper it pushes down the tongue of the keeper as it passes over the top. Once it passes over the top of the keeper, the keeper is released and reverts to its vertical position due to the weight of the duck bill. At that point, the gate is held in an open position until a person pushes the gate back and engages the keeper back down, to allow the gate to swing over and out of the keeper.