What constitutes a "bag"?

[metrogdor22]

Hi,

I see that Southwest offers your first and second checked bags for free, provided they're under  50lbs and 62" (L+W+H). I want to transport what is effectively some steel piping (long tube headers for anyone who cares to Google it) as a checked bag. Their shipping weight is 40lbs and the box they're in is 20x9x43 (72"). 

Here is my question:

How does Southwest define a "bag"? Can I remove my headers from their box, and wrap them into a bubble wrap and duct tape bundle that would fit in a 62" box (but not actually in a box), and call that my second checked bag?

[DancingDavidE]

Drop them into a golf bag and you are set!

I saw something about prohibiting cardboard boxes as checked bags on these forums, but that may have been specific to international travel.

As long as the item is within the size and weight parameters, and the baggage handlers will have a way to pick it up, and it is sturdy/secure for your items not to be damaged, I think this would work but hopefully you can get some additional replies.

These are for cars right? Maybe you can browse some car forums and see if someone there had the same issue bringing some headers as a checked luggage.