GAF roofing has a four nail pattern. The shingles come in 2 sizes: English and metric. In this video we will be using English sizes. Place the shingles in a row by row pattern. You may move left to right or right to left but never move up the roof. You may have the shingle hanging over the roof by 1/4 in. Install the leak barrier in high wind areas. Place the second shingle next to the first. Five inches of the underlying shingle should be exposed. Use a whole shingle for the first course. The second course should be trimmed 11 inches and the third course should be trimmed 17 inches. The fifth course starts over with a whole shingle. Continue this pattern. Every 6th course, draw a chalk line to check that the lines are parallel.