This is the bottom view of the Laird model MBO NMO mobile antenna mount.
In the center is the pin which connects to the coaxial cable inner conductor. The shield of the coax lays to the side and is clamped in place by the crimp tabs.
The foot does not cover the entire hole, rather it is rectangular to allow all installation from the outside. The tips of the flange nestle in the 3/4″ hole and over lap just a bit to grab the inside surface of the vehicle. It is these two tips, and their pointy teeth, that make part, if not most, of the electrical connection between shield and vehicle.
