The working mechanism
The under-gate movable extension basically consists of
a vertical pipe that can move up and down through the holes in two eye bolts,
two horizontal rods that are bolted to the lower portion of the vertical rod (per gate).
There is an arched foot welded to the bottom of the vertical rod.
When the gate opens, the arched foot slides on the driveway and when the gate opens over raised ground, the vertical rod rises accordingly, thus lifting the two horizontal rods.