To install a drip edge, measure all the outer edges of the roof, cut lengths of drip edges accordingly, and install the drip edge. Required tools and materials include a hammer, galvanized roofing nails, a ladder, a tape measure and snips.
Clean dirt and debris off the roofing before starting the installation. Measure the outer edges of the roof with a tape measure. Use the measurements to purchase the required drip edge. Cut it into pieces with snips.
Place one piece at the corner of the fascia along the eave, designate the angle of the slope with a pencil, and cut it as appropriate. Building toward the peak, raise the shingles; insert the flat flange of the drip edge under the shingles, extending the outer edge to the gutter. Secure it in place with a hammer and nails, leaving a space of 1 foot between the nails. Take care not to nail down the fascia. Replace the shingles as you progress.
At the end of each strip, place the bottom of the next strip over the top of the last strip to create an overlap joint, which allows runoff to flow over the joints to the gutter instead of draining underneath. Install the drip edge over the entire roof, and test your work.