In BDSM, hammers are sometimes used as heavy impact toys. The hammers used are commonly pervertables taken from the kitchen (meat tenderizing hammers), or the hardware store (wooden or rubber mallets). Hammers are used predominantly on the recipient's ass or legs, avoiding soft tissue, bones and joints.
There are some BDSM toy makers that make specialty hammers just for impact play. These are not common, however, and they tend to be lighter than their hardware store counterparts.
Safety Tips
Because many hammers would be considered "heavy" impact, it's important to be careful how hard you are hitting a person, as well as where you are hitting them. These toys can cause permanent damage, and should be treated with respect.
If using a meat tenderizing hammer, this could potentially become blood play due to the nature of the surface that is used for hitting. Because many of these hammers are made out of wood or other porous materials, these toys would be considered fluid bound to a person and not shared with others.
