Certain types of wood are sufficiently dense and hard to be used as hammers in percussion flaking.  As with antler and bone, these hardwoods are soft enough for the edge of the stone to ‘bite’ into, effectively transferring the force into the stone.  Wood is also preferred for some modern knappers as the hammer used to strike the punch in the indirect percussion technique.  These hammers are usually made of a softer wood than hammers used in direct percussion.  Wood was the most common material for hafting stone tools, but wood handles rarely preserve in the archaeological record.