A bucking bar is a dense, handheld metal tool pressed against the tail of a rivet. It acts as an anvil, using its own mass to resist the blows of a pneumatic rivet gun on the opposite side of the joint. The impact forces the rivet tail to expand and flatten, locking the plates together. Tungsten bars are often used in tight spaces because of their high density.
Heard on the job
Grab the offset bucking bar so you can reach around that stiffener.