UglyDan®©™ wrote:
Yep, Thats a needle gun, They serve their purpose well, but the needles
can leave pock marks on mild steel, The best way to avoid pock marking
the metal is to place the needles at 45 degree's to the surface.
I also wouldn't use one on anything made of cast iron. Just my 2 cents.
UD

Thanks guys,

As you know, a trailer is made (usually) of a lot of heavy, flat,
squared stock with little change in it's surfaces. With exception of
brake lines and fender, suspension supports, it ought to do well on the
majority of stuff. I haven't looked that much, but if I can un-bolt the
fenders. I'll do them individually, as well as the total frame. I might
look things over and wait till this spring, because I can dump the tub
off into my neighbors pond, and re roller the trailer and do it all at
once. But, thanks for the tip on angling the needle gun. I have seen
pics of them that do have the needles in an "upward" angle.