Abstract: A section mill is positioned below a whipstock or other exit guide in a drill string assembly used to mill a section of steel casing below the whipstock and which as the section mill moves down and mills along the section of casing, causes the whipstock to be lowered down adjacent the milled-out casing and allows the drill bit and drill string to be run along the surface of the whipstock and into the earth formation. In an alternative embodiment, the combination of having the section mill below the whipstock is used in open hole operations having no casing. In yet another alternative embodiment, the section mill is positioned above the whipstock or other exit guide in a drill string assembly after the section mill has milled out in an appropriate length of the steel casing, the tubing string pulls both the section mill and the whipstock or other exit guide up to a position where the exit guide is adjacent the area of formation which has been exposed by milling along the steel casing.