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 Center Kit lifts both center wheels when planting. Before the Terrace King Center Kits, the two center wheels cause rows to lose ground contact near the hinge points.After the Terrace King Center kits, the row units stay in the ground as you plant up and over terraces.