A small piece of card (maybe from a cereal box) or other similar slim item (i phone?) placed between the testicles of two lucky men giving an even luckier woman some double trouble. The board is for the less adventurous or shy man who doesn't want his balls slapping against his mates and prevents 'skin to skin' or 'bollock to bollock' contact. Could even prevent premature ejaculation for the more adventurous who enjoy said skin contact.
Rodney always dreamed of a threesome with the neighbors, but as a shy man worried about his balls making contact with Colins. Simply drawing round his testicles on an old Weetabix box and cutting out the shape gave him the perfect made to measure Bollock Board.