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Overall view of the shoe.

Picture 4 of 4.

Note the triangular cleat on the ball of the foot.

This shoe appears to be an early prototype, as the cleat differs from those actually worn in flight (scroll down to the tenth photo for a view of the bottom of the shoe).

In particular, the flight shoe allows the cleat to be repositioned anywhere along a track from the ball to the arch of the foot, and the triangular cleat has a wingnut. This is presumably to allow the cleat to be positioned in the track, and I speculate that it may allow the cleat to be removed (e.g., in case it were to get stuck in the grid).