I used to have an old J.C. Higgins tent trailor (had no tent) for hauling my camping stuff, the whole trailer weighed like 150 lbs.
The guy I got it from used it to haul racing bicycles and as a support trailer in 'centurys'.
Any way it had like 50 1/2" holes drilled in the top where all the bike racks and such were mounted, I used that stuff to plug the holes.
Clean the area w/non ferrous (brass?) metal brush, melt a puddle of the rod next to the hole swipe the puddle across the hole with the rod, sealed tighter than a drum.
It can also be used to build-up and reshape the leading edge of aluminum boat propellers, tough stuff. Llke a cross between brazing and soldering, low temp.
Norm