[andrewflnr]

What are they supposed to do? Can you weld them on somehow?

[ferongr]

Hooks, holes in the backing plate, stamped/cast dimples, welded wire-mesh for the backing material to adhere to.

[andrewflnr]

Ah, so glue plus mechanical linkage, if that's the phrase?

[Hatrix]

rivets

[SoftTalker]

This is how it was done for years, they have better adhesives now. In modern cars many of the body panels are affixed with “glue.”