When welding thin gauge, avoiding weld through can be (is) tough. Using a heat sink can help. On cars, having a piece of thick aluminum behind the 20 gauge steel can help. It won't prevent it, but one reason to weld on a metal table is to dissipate heat. Same principle.
Is this trouble while using MIG or TIG?
In reply to Woody (Forum Supportum) :
This!!
Hmmm. I have copper pipe, pop rivets and Gorilla tape. Ta-dah. That looks like a good idea to have around. I'm gonna have to make that
This is for welding holes shut or what ever else you can come up with