Will these work on carpets as well as hard, smooth surfaces?
Any surface that can offer some amount of traction will do better than ones that are very slick. Hardwood floors are not the best option for pull toys most of the time. Thin carpets work the best because they offer traction, but do not impede the rolling of the wheels of the toy. Small rugs or towels can always be put down on slick surfaces to help with the movement of the pull toy.