How to Locate a Truss From the Shingle Side

Examine the blueprints. Find the heel points of each truss on the blueprint. Heel points are the lowest point of the truss, located at the outer edge of the roof.

Identify the distance on the blueprint from the end of the roof to the first heel point. Measure in toward center, the distance on the roof itself and mark it with an "X", on the shingles, in chalk.

Walk three feet up the roof. Measure in toward center, the same distance from the end of the roof. Mark the spot with an "X" in chalk. Walk up three more feet and repeat until you reach the top. You will end with a vertical row of "Xs" all the way up the roof.

Have an assistant hold a chalk line flush with the shingles at the heel point. Walk the other end of the chalk line all the way up to the peak. Align the chalk line with your marks. Snap the chalk line on the shingles to create a visible line of chalk that connects all of the marks. This chalk line represents the location of the first truss.

Repeat the previous steps to outline all of the trusses. Use a hammer and tap into the roof on the chalk line. Listen for a clacking sound to indicate your are hitting into wood, which is the truss. If you hear a hollow "bong" sound you are between trusses.