Novarider wrote an answer about Thule Insta-Gator Truck Mount on August 13, 2013
The anchors appear to be made out of reinforced hard nylon plastic. Where they fit into the tailgate there shouldn't be any visible damage if it caused any. It wedges between the bottom edge of the tailgate and the leaded edge of the bed. It becomes locked in place when the tailgate is latched shut.