Auto convex collision

This option is used to create much more accurate collision shapes for your models. Once you click on this option, a new dock window appears at the bottom-right corner of static mesh editor; using Max Hulls (the number of hulls to be created to best match the shape of the object) and Max Hull Verts (which determines the complexity of the collision hulls) you can create more complex collision shapes for your Static Mesh.

As you can see in the following screenshot, the auto convex result is reasonably accurate:

Tip

Collision shapes support transformation (move, rotate, and scale) and you can duplicate them to have multiple collisions. Click on the collision shape inside static mesh editor and you can switch between move, rotate, and scale using W, E, and R. You can use Alt + left click drag (or Ctrl + W) to duplicate an existing collision.