Youll have seen and perhaps used a step stool like this in a school library or office for decades workers have depended on the step to reach high shelves to retrieve books files medicines and more the principle is simple the step rolls along effortlessly at the lightest nudge of your foot but step on the platform and the three spring loaded castors will retract ensuring the rock solid rubber base grips firmly and immovably to the floor the body of the retro step comes in two easy snap