Set up your extension ladder. Lay it against the house at a 75 degree angle. Raise the ladder so that the top rung is three feet above the top of the horizontal gutter on the house.
Clip a painter's hook onto the handle of a five gallon bucket. Place your drill, bits, rivets and rivet gun into the bucket. Tie the free end of the rope to your work belt.
Climb the ladder until you are looking down into the horizontal gutter attached to the house. Pull the rope and lift the bucket under the ladder. Keep one arm around each side of the ladder for balance and safety. Lift the bucket until you can grab its handle. Hang the free end of the painter's hook onto one of the upper ladder rungs with the bucket hanging under the ladder.
Drill a hole through gutter 12 inches from end with 1/4 inch bit. Widen this hole by drilling into the same spot with your 4 inch hole saw.
Coat the upper rim of this hole with silicone from your caulk gun. Slide the neck of the downspout outlet into the hole. Hold the upper rim of the outlet firmly against the inside of the gutter. Drill a 3/16 inch hole on each side of the outlet. Make each hole through the outlet as well as the gutter itself. Slide the head of a rivet into each hole. Slide your rivet gun over the shank of each rivet and squeeze the handle to lock the rivets in place.
Slide an elbow onto the neck of the outlet under the gutter. Drill and rivet the elbow in place. Cut a piece of downspout with your tin snips. Make this piece long enough to go from the elbow to the side of the house. Slide the piece over the open end of the elbow. Drill and rivet the piece of downspout to attach it to the assembly.
Attach an elbow joint to the bottom of the downspout. Cut a piece of downspout to fit from the elbow to a point 6 inches above the ground. Drill a hole in each side of the juncture and rivet it in place.
Attach a final elbow to the bottom of the assembly. Leave the open end of the elbow pointing away from the house.
Place a downspout strap around the assembly. Drive a masonry bolt through the hole in either side of the strap and into a masonry joint on the side of the house. Place a strap every three feet up the side of the house to secure the downspout assembly to the wall.