What keeps anchor bolts from pulling through?

Anchor bolts are required to have an anti-pull out device generally this is a washer with a nut that is tack welded on the end so it cannot be unthreaded.

What keeps anchor bolts from pulling out?

Anchor bolts are required to have an anti-pull out device generally this is a washer with a nut that is tack welded on the end so it cannot be unthreaded.