One of the first steps of roof installation of an asphalt shingle roof is to install the drip edge. Starting at the eves, install it toward the middle of the roof. A simple cut in the drip edge will allow it to fit over the ridge.
The drip edge is installed first so that no water will get between it and the roof. When nailing it down, the nails should never go through the front flange. They should go through the drip edge and then into the decking. Then, the felt is installed. This goes over the drip edge so that water won’t collect there.
The felt is held down by plastic caps. The caps should be about 8″ apart in areas that get a lot of wind. In areas that don’t, it’s fine to have them 16″ apart. There is another layer of felt that is put over the ridge, and it sits on top of the other layers. A starter strip is then installed along the edge of the whole roof. This strip should be about 1/8″ further out than the drip edge. The shingles are later installed another 1/8″ out so that the roof has an overlap of about 1/4″.