When removing a branch at the point of attachment the goal is to remove the branch as close to the trunk as possible without cutting into the branch bark ridge or leave a stub. The diagram below is numbered in the ideal order for removing a limb that is best for the tree and safe for the pruner.
(1) Make a cut on the under side of the limb several inches from branch union. This will keep the weight of the limb of the from striping bark down the tree.
(2) Make the second cut on the top of the limb above the first cut, removing the majority of the limb making it more manageable to make the third cut properly.
(3) Remove the remaining stub just outside the branch collar. The cut should leave a smooth surface with no torn bark or broken edges.
Branch Collar - The swollen collar develops around the base of a branch at the point of attachment. The collar is formed by overlapping wood from the trunk and branch making a very strong union to hold up to wind, snow and other forces. Inside the branch collar a chemical barrier called the branch protection zone which function is to stop decay and other pathogens entering the tree.
The brach collar is common in most species however not all are swollen and visible, some tree species do not develop the branch protection zone leaving them open to pathogens after pruning.