Merco manufactures so many different types and sizes of hoops that all have their own mounting plate but most of those were designed for wood dock. You can use the TF-DPSP by itself and it has slots to attach a roller assembly but when you mount the roller assembly on the face of the plate you lose 2-1/4” off the length diameter of the hoop. That’s where the TF-ADAPTER comes in. The adapter allows the roller assembly to be mounted to the top of the dock, just like all of our other hoops. The long slots in the face allow for several different sleeper and decking setups. The adapter works using anything from 3/4” plywood, all the way up to 2x4 sleepers and 2x6 decking (totaling 3”).