Abstract: Siding boards, shingles, shakes, or the like are applied to the wall of a building by use of a tool having an arm which extends upwardly adjacent the wall structure and is temporarily secured thereto, with the siding or the like then being placed at the outer side of the tool arm, and being supported at a predetermined level by a projection extending outwardly from a lower portion of the arm, so that the siding can then be nailed to the wall structure and the tool can ultimately be withdrawn from its position of reception between the siding and wall structure for use in similarly positioning and securing a next successive layer of siding, shingles, etc. to the structure. Preferably, two such tools are employed at horizontally spaced locations for supporting the siding or the like therebetween.