The way cuts are made when trimming a limb helps keep trees and shrubs healthy.
With a bypass lopper, you want to leave the collar, the swollen ring at the branch's base. Any cuts in the collar can cause poor or slow healing, and that can lead to rot. Start with a razor-sharp cutting blade and position it (not the blunt counter-jaw) where the collar meets the branch. Squeeze the handles for a clean, crisp cut.