GND on the sides of PEPWAVE MAX

What are the two GND screws on the side of the PEPWAVE for? I assume ground but for what?

I always assumed that when you have a serial connection from the MAX to another device (like a 3rd party managed switch for out of band management) that its wise to make sure that both devices are tied to the same ground so there is less chance for ground leakage / voltage potential between devices over the serial bus.