Abstract: In a method of making holes of selective external configuration in a rock or earth formation, two or more rotatable drills provided with drill crowns are driven into the ground. The drill crowns are so arranged that they will touch each other or are radially spaced a small distance from each other and are substantially on the same level. The drill crowns are simultaneously axially displaced while they are rotated each about its own axis only. The drill crowns sit on drill rods provided with guide means such as tubes which are driven into the ground substantially simultaneously as the drill crowns. The guide means may be connected together to form a single common guide structure. When drilling two or more holes situated adjacent one or more previously drilled holes, a guide means having spacer means is inserted into a previously drilled hole, said spacer means guiding the drill for the further holes relative to the previously drilled hole by engagement with the residual walls of the drilled hole.