There are a series of menu options in the Static Mesh Editor under the Collision menu entry, named ##DOP, these are the K-DOP simple collision generators. K-DOP is a type of bounding volume, which stands for K discrete oriented polytope (where K is the number of axis aligned planes). Basically it takes K axis-aligned planes and pushes them as close to the mesh as it can. The resulting shape is used as a collision hull. In the Static Mesh Editor K can be: