A laminate-flooring bar fits under replacement shingles in places where a hammer won't reach.
Whenever there’s not enough room to swing a hammer, such as when replacing shingles close to a deck or intersecting roof, I use a laminate-flooring bar to tap the shingle into place. See the drawing above: I hit the flooring bar at the top (1) and it drives the shingle up from below (2).
—Aron Jones, Grand Manan, N.B.
Edited and Illustrated by Charles Miller
From Fine Homebuilding #291