A Thonet cantilever chair is specially produced to allow a retrofitting with plastic glides (transparent or black) with or without felt insert using the pre-punched drill holes, add an additional 11 mm to the overall height and cost 29,- EUR per set / chair.On older cantilever models produced before 2010, the Thonet frames were pre-punched as standard and the glides are installed as follows: With a 4.2 mm drill (available at any hardware store or as the special-hardened Thonet drill bits for Euro) bore holes in the marked locations. The felt pads can then be attached using the supplied self-tapping screws.