I'm cognizant of the frailties of the lap weld Robert. My reply was to point out that the impression the thread was giving, that factories don't use lap joinery, may not be accurate. My experience with rust has been that far more of it is caused by blocked weep systems retaining debris and moisture than lap joinery.

Save a life, adopt a senior shelter pet.
The three main causes of blindness: Cataracts, Politics, Religion.
Name your dog Naked so you can walk Naked in the park.