The tri-slot design offers great flexibility, allowing for the combination of various load accessories that can be used independently or together. In the top track, you can fit accessories like the Thule Load Stop, Thule Ladder Tilt, or Thule Ladder Holder. Each accessory mounts in seconds; just slide it in and lock it in place. The rear track easily accommodates accessories such as the Thule Roller, Thule Foldable Load Stop, and Thule Eye Bolt, or they can be mounted together. This keeps the top of the Thule ProBar free for your load.