The upholsterer's hammer is a relatively light (approx. 200-400 g) hammer - distinguishable from the glazier's hammer - with a long (approx. 10-15 cm), narrow (approx. 1-1.5 cm) head attached to a wooden stem. The hammer head has one round face and a flat pin at the other end, often with a claw.
The upholsterer uses the hammer to hammer in and remove tacks. Sometimes the head is magnetized; this way the nails are held in place, which makes work easier as furniture upholstery often involves nailing in awkward corners. [MOT]