It's a weight distribution hitch. It's designed to be used with spring bars of varying stiffness (weight capacity ). The bars are anchored to the frame with either chains or a bracket of some sort. When the rear of the truck squats, the bars attempt to angle farther downward. The chains or brackets prevent this and the bars will act as a lever to push more weight onto the front of the truck, counter acting the lifting that occurs when you apply weight behind the rear axles. Some weight will be taken off the rear of the truck and some will be transferred to the front wheels and the trailer axles. The angle adjustment allows for fine tuning it to increase or decrease the amount of tension on the bars ( and therefore, the amount of leverage applied ). The more downward the angle, the more weight transfer.
2012 Chevy Tahoe LTZ - HD tow package
2017 Rockwood 2703WS Emerald Edition