The vertical dock bumpers are recommended when you choose to tie the lift to the dock. The dock bumpers prevent wear of the tanks, and prevent the lift from floating under the dock when submerged.
The "Slide Assembly" mechanically connects the lift to the dock. It provides for multi-directional movement, while holding the lift at a fixed distance from the dock.
This is a popular option for sandy bottom lakes. A screw anchor on the end of a 12' galvanized steel poke is screwed into the bottom. The PVC assembly allows vertical movement, protects against tank wear, and provides a location to tie the lift to.