Measure the perimeter of your house. Add an extra foot to your measurements to account for cutoff. This measurement is the amount of shingle mold in linear feet you will need to install shingle mold on your house.
Begin on the front left corner of your house. Set the miter saw to a left 45-degree angle. Place the left end of a trim board on the saw with the 2-inch, or widest side, facing out. The narrow edge should face up. Cut the trim board with the saw. You do not need to cut off more than 2 inches.
Set the miter saw to a right 45-degree angle and cut the opposite end of the trim board. The trim board should be set in the same position with the narrow edge facing up and the same 2-inch side facing out.
Place the trim board so that it is flush or even with the top of the fascia board and the shortest point of the miter cut is even with the end of the fasica board. This will leave the longest point of the miter cut sticking out past the corner. Use the finish nailer to secure the shingle molding to the fascia.
Set the miter saw to a right 45-degree angle and cut the left end of a second shingle mold board. After cutting the left end, cut the right end of the same board with the saw set in the same position. Line up the left end of the shingle mold board with the right end of the board that is nailed to your house. The right end of the first board will slightly overlap the left end of the second board. This is called a scarf joint.
Nail the second trim board in place. Continue cutting the ends of the trim or shingle mold boards at right and left angles and nailing them in place. When you are finished, caulk all joints and the underneath edge where the bottom of the shingle mold rests on the fascia board. Prime and paint to protect against rot.