The 1907 farm house we're remodeling had handrails that are much
shorter than those used today. The arrow in the above photo shows
the original handrail attachment point. So the newel posts we bought
were 6 inches too long. But we could not simply cut them shorter
because they had a rectangular notch cut into the lower end for
mounting purposes.
First I cut 6" off the bottom of the notched post.
I set the circular saw to cut the same depth as
the original notch.
I cut a kerf 6" upstream of the original
notch.
I made a lengthwise cut on each side of the
post.
I finished the cut with a hand saw.
The two longitudinal cuts did not quite align
perfectly (due to inaccuracies in the saw base), but this did
not pose a problem.