The picture above is the picture of the handsaw and as we
all know handsaw's go back in history a long ways. Your grandfather or
great-grandfather's use handsaw is to build most of their projects
before power tools.
The handsaw is a great tool when building stairs for cutting in tight spots where you can't get a circular saw or other power tools into. The handsaw can also be used to finish the cut on the stair stringer to give it added strength.
For example when you're using a circular saw and cutting the stair stringer you will come to a point where you can choose to run the saw a little bit farther and weaken the stair stringer or you can use the handsaw to make a nice clean square cut as shown in the picture above.