The scenario can begin in different ways. One involves you pulling the shoes, trimming the feet and noticing a small cavity just inside the white line. Picking up a nail, you give it a scratch and a powder-like substance comes out. More scratching leaves you part way up the hoof wall. Another involves having a horse with hoof walls separating in the most distal part of the foot. While probing the separation, you discover that not only is it separated at the bottom, it goes much higher.