Mark the center of each section and use a compass to mark 30 degree angles along the sides of each.
Roofing using half tab method.
For example if you re roofing from left to right align the first shingle of the second course so the right side of the shingle.
Three tab shingles are most typically installed with a half tab offset that yields the characteristic brickwork appearance.
Check them with a framing square or measure so the lines are parallel with the rake ends.
Set the first shingle of the second row back a half tab 6 inches 17 centimeters from the edge of first shingle on the first row and so that the bottom of its tabs just touches the tops of the cutout slots on the shingle below.
The cut outs separating the shingle tabs line up every other course.
This 1 2 tab has to be cut off where it hangs off the left edge of the gable roof.
The simplest way to do this is to use the half tab offset method.
Use a heavy duty utility knife to separate the shingles into thirds by cutting them at each tab.