In one sentence, describe what the following article is about:

Measure 2–3 feet (0.61–0.91 m) from the leader, or the main vertical stem of the tree, then place your hand or pruning saw against the underside of the branch. Move the saw back and forth to cut a notch 1/3rd through the underside of the branch you want to cut.  Cutting a notch in the branch will protect the bark from breaking apart. If you’re cutting smaller branches you don’t have to cut a notch and you can use hand pruners. This relief cut will prevent the branch from breaking and splintering when you make your final cut. Measure 6 inches (15 cm) down from the notch and use a saw to cut off the end of the branch. After making your relief cut, your branch should be a nub with a notch cut into it. Make sure that the area under the branch is clear of people and objects. Find the branch collar, which is area of the branch where the rough bark turns into smooth bark. This should be a couple of inches away from the leader. Keep the branch collar intact when you trim so that the tree heals fully. Use your handsaw to cut off the remaining portion of the branch. Don’t cut the branch too close to the leader or it won’t heal properly. Over-pruning the tree could weaken it. Whether it’s a young or mature tree, avoid cutting away a lot of the branches at once. If you want to cut down a tree significantly, you’ll need to spread the pruning out over several seasons.

Summary:
Cut a 2–3 inches (5.1–7.6 cm) notch into the bottom of the branch. Cut through the branch 6 inches (15 cm) from the notch. Cut the branch off the leader. Don’t prune more than 10%-15% of the foliage per season.