This depends on the machine you’re using. Models like the Auxfun Sex Machine uses suction cups to keep it in position, so it needs to be right up against the floor in order to work properly. The Hismith Table Top 2.0 Pro has small rubber feet that hold it in place without damaging the surface, so you need nothing underneath it. The only issue may be with models like the Cloud 9 F-Slider Ride-On Sex Chair, which has no such protectors, so you may want to put it on a mat or towel to keep it from scratching the floor as you use it.