A plumb centerline snapped on the gable wall guides shingle-panel installation.
Next, the base course for the first course of wave shingles is tack-stapled to the wall.
Wide shingles simplify the two-course transition between installed shingles and the base-course shingles before the wave pattern starts.
After the first of the two interceding courses is installed, the base-course shingle strips have to be removed in order to install the second course of straight shingles; marks show where the shingle joints of the base course land.
The joints on the second course of straight shingles have to be offset from both the joints in the first course and the marks indicating the base-course joints.