In the left photo, you can see the bracket that has padding on it. These swing out when in use, and swing parallel to the wall when not in use.

In the photo on the right, you can see an overall photo of the system. At the top, the "Carabiner". It is in the shape of a "D" usually, and has a gate which opens and closes. When Ed stores his kayak, he swings out the mounts, and uses rope to hold the kayak against the wall. The Carabiner makes an easy way to connect and disconnect the rope. Low cost and extremely functional, you bet.
Photo's courtesy of Ed Whited.