Abstract: A combination tool includes a retractable knife and a pitch gage which provides pitch measurements directly in terms of inches of vertical rise per foot of horizontal distance. The tool can also be provided with indicia to permit vertical and horizontal alignment of shingles, as well as uniform overlapping of boards, and a liquid level device. The tool has a casing with a storage compartment for holding extra knife blades or different types of knife blades. A method is disclosed which permits the tool to be used for obtaining uniform shingle overhang, horizontal and vertical alignment of the shingles, and uniform overlap of siding boards.