dsc00806.jpg

Detail of the triangular shoe cleats.

Note that there's a wingnut at the center of the cleat. Presumably, this allows the cleat to slide along the track, allowing the astronaut to reposition the cleat anywhere from the ball to the arch of his foot, as may be personal preference. I also speculate that it may allow the cleat to be removed entirely (e.g., in case it were to get stuck in the grid).