How to replace a few missing shingles?

To replace a few missing shingles, you can do it yourself if the roof is low-slope, easily accessible, and you are comfortable working at height with proper safety gear. First, gather materials: matching replacement shingles, roofing nails, roofing cement, a flat pry bar, hammer, and utility knife. Safety first, use a roof harness and work on a dry day. Start by removing any remaining damaged shingle pieces. Slide the pry bar under the shingle above the missing area to gently break the sealant strip and remove nails holding the damaged shingle. Carefully remove nails from the course above that penetrate the missing shingle area. Slide the new shingle into place, ensuring it aligns with the existing pattern and that its top edge is under the shingle above. Nail it with four roofing nails, placed about 1 inch above the cutout slots and below the sealant line of the course above. Do not nail through the exposed part of the shingle. Apply small dabs of roofing cement under the overlapping shingle above to reseal it, and press down firmly. Apply a small dab of cement over nail heads that are exposed. For the last shingle in a row where you cannot lift the shingle above to nail, you may need to face-nail it and cover the nail heads with roofing cement. If the damage is in a valley or around flashing, call a professional.