The gate in the top pictures seems like an odd one. It is only actually attached to the gate by the top hinge. The bottom is merely leaning on the gate. I've drawn a force diagram at the bottom. Only the top hinge is needed to produce a normal reaction force N to hold up the gate. The bottom hinge pushes on the gate with a force R to create a moment that is equal and opposite to the moment created by the weight of the gate. The contraption at the bottom is there to keep the gate in place as it turns.
