What is oil canning?

Oil canning is the waviness of light gauge metals and is a natural characteristic of the material. 

Oil canning is the waviness of light gauge metals and is a natural characteristic of the material.  Oil canning is more evident in lighter gauge metals with large, unsupported flat areas.  Oil canning can be minimized by reducing the dimension of flat areas and introducing stiffeners and/or embossing patterns to help reduce its appearance.