slap hammer noun a hammer designed for pulling dents but used to break open the top of a car’s steering column to obtain access to the ignition US
He told them he’d spot the car a customer wanted and use a slim jim or lemon pop to get in, a slap hammer to yank the ignition, a side kick to extract steering column locks and usually liquid nitrogen to freeze the alarm system. — Elmore Leonard, OutofSight, p. 56, 1996