Rubber or soft plastic caps, or feet, are fitted to the end of each leg. These components are called 'ferrules'.
Ferrules reduce the chance of stools slipping on hard surface flooring.
As perching stools are also used at the bathroom sink, where floors are often wet, this is an important feature.
Some stools feature ferrules with angled bases, meaning they contact the floor at an optimum angle to maximise contact and friction.