The Caster Wheel kit can be used to convert a crate into a rolling crate. The kit comes with four casters (two that are stationary and two that swivel and lock into place). Each caster comes with a slide-in bracket that bolts to the crate bottom. To remove the caster, push down the tab, located on the bracket, and slide the caster off. The brackets come with the hardware bolts and acorn nuts. The rounded acorn nuts prevent a dog from hurting itself on the bolt.