The Foot Shack is a front business for the Foot Clan in Rise of the Teenage Mutant Ninja Turtles. To those unaware of the Foot Clan, it appears to be an ordinary store devoted to shoes and T-shirts, albeit one with some odd decorating choices such as shuriken.
However, a massive round vault door is placed on the rear wall of the store, which leads to a large rear chamber in which the ninja clan does its more secretive business. The rear room also has a secret descending staircase that allows the Foot Clan to enter a massive subterranean cavern under the store.
The Foot Shack first appears (timeline-wise) in "Shadow of Evil", shortly after April O'Neil has become employed there.