A shingle mounting system includes a plurality of securing strips for detachably securing shingles to a roof surface. Each securing strip includes a base portion, a folding edge, and plural projecting members attached to the base. Each shingle has a line of perforations formed through an upper edge thereof. Shingles are attached to the securing strip by placing the projecting members through the holes in the shingles, and folding the folding edge of the securing strip over the base portion. A roofing kit according to the invention includes shingles, securing strips, and at least two adjustable spacer tools. Each of the tools includes two channeled pieces that are slidably nested one inside another, and which may be locked in relative position via a locknut assembly. The tool operates to measure spaced placement of the next securing strip, eliminating the need to hand measure spacing of each succeeding shingle row.