My former Dahons both used a protective "shield" (actually a tennis ball can cover) on the bottom of their seatposts which was similar to my present Brompton's Seat Pillar Rubber Bung-defined as a....."useful part fits into the lower end of the seat post. When the Brompton is folded, the bung retains contact with the ground to prevent the bike from rolling away on a slanted surface...." I mainly use it on all those bikes as prevention from marking floors and walls just as you intend to do.