The Terrace King is a modified carrier arm that lifts the wheels above the ground when planting, but returns them to a weight-bearing position when the planter is lifted. 

The wing kit lifts the inner wheel when planting. Before Terrace King, the inner wing-wheel causes row units to lose ground contact at the end of the wing when planting. After Terrace King, all row units are in the ground and planting

Here is a side by side comparison of how Terrace King fixes a common problem of row units not planting as the planter goes up and out of the ground.