floor pan drains?

[VintageAutobahn]

I have been reading up on previous floor pan posts and there is somethingw that I am a bit confused about, why do people weld the drains in?I will be welding in some patches but am curious why/if I need to weld these things in. Also should I have a bit of overlapping metal when I do weld in my patches? If i do overlap the patch is it better to do it from the top or the bottom? TIA for all your help guys

[JackF]

When I replaced the pans in the 72 I went with the whole front left and right replacement pans and the plugs are deleted when those pans were pressed. Both back plugs were loose and there was corrosion around their edges. They were for production purposes only as if they were installed and tight they pretty much held water anyway. Every gasket that can leak water into the interior has been repalced and the pan repainted on my car and the I consider it to be an improvement over the original.

As to how to weld it, what I did was to cut a heavier metal plug. I think I used 12ga. If the margins of the plug hole are thinned out due to corrosion it is a tad dicey getting the metal to co-operate so form your plug accordingly. With the 12 ga I had enough body that I could carry my heat on the heavier metal and just walk over to do the tie-ins without blowing everything away. Much easier to wled and I think I also backed up the factory metal with a section of thick copper buss bar. I POR 15'd the pan and the second time it came out great.