Abstract: An alignment tool for positioning square tab shingles on a roof surface in perfect alignment with shingle strips already fastened to the roof includes a long, straight shingle positioning plate having a base flange and an unfastened shingle positioning flange extending at right angles up away from the base flange. Two clamps extend back from the base flange, each clamp having an upper jaw mounted to the positioning plate and a lower jaw pivoted to the upper jaw. A bottom row positioning stop is located between the jaws of each clamp. The lower jaw of each clamp is slid underneath the bottom edge of a shingle in the top row of fastened shingles until that edge is in contact with the positioning stop. Unfastened shingles are then positioned with their bottom edges against the unfastened shingle positioning flange, the shingles are butted against each other, and then are ready to be nailed or stapled into place.