Sometimes called "Goosing". To poke someone in the bum hole, no penetration required. This is done on the outside of the clothing. Usually done with a broom stick. The intention is not to draw blood, but rather to make someone jump. Could be considered sexual harassment.
Two brothers are putting up a tent. Brother one drops a tent peg, and bends at the waist to pick it up. Brother two pokes brother one in the bum using he butt of his hammer. This act is a corn dog. No one is hurt. Both laugh. In the future, brother one looks behind him before bending over.