Wondering why there is a need for a sheet metal door? Some are not heavy duty. There are many traps with escape proof wire mesh doors that are plenty strong, much stronger than some solid metal doors that as Paul mentions could be twisted, bent and would allow a coon to escape. Its not just the door material in the door, but how the door is hinged and constructed that is important. Most traps still have clipped hinges that can break free over time. Others have quarter inch rod wrapped around quarter inch rod. Some wire panels are clipped with 15 gage clips, some metal bands and or 12 gage clips, while others have wire mesh that is welded to quarter inch framing. Lock bars can be flimsy. I have seen pictures of coon twisting doors where the lock bars were cheesy. Though a gravity door trap works, gravity traps should be longer, larger, to prevent back outs as animals can beat the door. With powered doors, much shorter traps can be utilized to do the same job as a longer gravity trap, take up less space in the truck and are easier to place because they are smaller. When skunks are trapped, metal or plastic covers will keep them from spraying, protect bait and can used in positive sets to catch denning animals coming or going from under sheds, porches or under fences.