The newel posts come in two main varieties: solids are normally fitted with metal stair rail brackets L box and needing a wooden support block installed inside of the base to anchor it to the floor. The keys to perform well the project are to measure carefully before cutting the bracket and secure it to the floor well. Place the stair railing in place before mounting your post to ensure a proper connection between the rail and post. Give back to the post so that the open base is exposed. Use a tape measure to measure inside the base, side to side. Measure each direction at each corner and in the center of the post. Record your measurements over small in each direction.
Use a framing square to a square on a piece of wood 2 inches (5.08 cm) thick, with measures of the dimensions more small stair rail brackets inside the post. Keep square corners. Cut the mounting block with a miter to make sure the corners are straight.
Place a bit on the cordless drill and adjusts the chuck. Measure and mark the mounting stair rail brackets to one inch (2.54 cm) of each corner in both directions. Beam guide holes in each of the four locations throughout the drill block with 1/8 inch (3 mm).