Hobie wheelcart collars. Wheelcart collar clamps help to ensure the weight from the kayak doesn't cause hull deformation from resting on the wheelcart crossbar.
Positioning the bushings is simple. Place the kayak on the ground upside-down. Slide the cart into the scuppers. Position the bushings against the bottom of the scuppers and tighten. Re-check that the cart posts fit clear through the hull.