Next cut and nail the front upper rail (M) and the lower rail (N) to the subrails. Both ends should butt tightly to the side trim.
Cut the small doorstops with a handsaw and then glue and nail them to the edges of the subrails. With the doorstops in place, set the doors into the opening.
To make the trimming easier here, cap the ends of the short walls with trim, and then install the lower 2x4 subrail over the trim.
15 Trim the inside faces of the 2x4 frame, then install the lower 2x4 subrail, baluster assembly and trim.
Measure each space and cut the rails (E) and the
subrails (S) to fit.
Some of the balusters, rails and
subrails will be new parts; some will be replacements for those that didn't survive the demolition phase.