Then you have to use a hammer. Open the skeleton on the back of the cover and knock it out bit by bit with a hammer.

After knocking, close the opposite skeleton. If there is no skeleton at the impact position, just knock it out.

Like EVO's headgear, it's over when you hit it. If it is very slight, it can be hammered flat. If the area is large and folded, there is no way out. The sheet metal machine is helpless for both iron and aluminum, and the aluminum is easy to break after secondary leveling, so it can't be done.