To paraphrase beyond nipples there is also:
The forces of friction enhanced by the nature of the cantilever supporting those forces manipulated to be downward with no apparent vertical or rearward structure by discrete engineering with a very small factor of safety which is in most cases hung on cantilevers divided in two, thus f/2 acting upon the supplied cantilever.
Exact measure of forces would require close study of said cantilevers. However as no volunteers have as of yet been found, exact measures of forces can not be provided.
— lates
— jrawk