Metal hammer with a short handle and a straight or curved hammer head with square faces. Sometimes hollows have been deliberately made in the sides above the handle. (1)
The stonemason uses this hammer to hit the narrow-headed chisels (2), a crown drill or a masonry drill). Also when splitting off a block of stone of the right size and shape; one by one a number of wedges are then knocked into the block of stone in a straight line and some distance apart until the two parts of the stone are split apart.
See also metal carver's mallet. [MOT]
(1) These cavities would ensure a better distribution of the impact force on hard stone types such as granite (MERCUZOT: 221).
(2) When the chisel head is wide, a wooden stonemason beater is used.