The scrotum is an integral part of the male genitals. It is a loose sac of skin containing the testes in mammals. The scrotum varies in length with some hanging longer than others. The scrotum is between the penis and the anus. When the male penis becomes erect, the scrotum often is presently more distinctly away from the thighs.
In consensual spanking, a spanking position may present the scrotum, which may heighten erotic feelings of spankee and spanker. In the knees-and-chest position, for example, male spankees may present the scrotum hanging below the buttocks. A skillful spanker can play with the scrotum without causing any harm to the scrotum or testes. A spankee may protect the scrotum by keeping the knees together or by wearing a thong or jockstrap, which still presents the naked buttocks.
As with any spanking and BDSM play, the sensitive scrotum is subject to negotiation between the players.