This gate was designed by Humble Oil Engineers in the '20's ??? because they hated to get out, open the gate, drive through, get out, close the gate, and ditto on the return trip.
To the bottom right of the gate, there is a wood bumper strip. To pass through the gate, the driver eases up and taps the gate with his front bumper, and the gate swings open to the left, winding the chain around the pole ( hopefully not so hard as to to swing it around and wipe out a left tail light). If he didn't tap it hard enough, it left a nice scratch down the side of his truck.
After passing through, the gate swings closed on it's own when the chain above unwinds. It works the same going out.