1. Start by identifying structural parts of the stair that could be used to attach additional fasteners from the railing to the stairs. The stringer is usually at least an inch thick on the edges of the stairs. Look for nail holes in the treads to help find it.
2. Plumb up the newel post by holding a level up to the side. Once it’s in the correct position, use a 2×4 or other piece of scrap wood against the wall and the post to hold it in that position. Place a few shims both on the wall and on the post in between the board to prevent it from scratching or damaging either surface.
3. Measure and mark the location for the screws, ensuring that they will hit the stringer when screwed in.
4. Drill into the post from the front using a forstner bit a few inches in to act as a countersink to hide the head of the screw.
a. Nathan recommends measuring and marking the desired depth ahead of time with a little bit of painter’s tape on the drill so it’s easier to determine when to stop drilling.
5. Using the 3/16” drill bit, drill into the hole just created by the forstner bit, through the post, and into the stringer. This will help prevent the screw from splitting the wood once it starts driving in.
a. Nathan recommends using a framing square against the post and the drill bit to ensure you’re drilling straight.
b. Like before, measuring and marking the depth on the drill bit with some painter’s tape can be really helpful here.
6. Drill the structural screws into the post.
7. Apply wood glue to the ¾” dowel and use it to plug up to the two holes left behind from the screws.
8. Cut the dowels so that they are flush with newel post using a Japanese pull saw.
9. Lightly sand the dowels until they’re smooth against the post.
10. Paint over the dowels so they blend in with the rest of the post.
6-inch structural screws
2×4 scrap wood
¾-inch wood dowel
220 grit sandpaper
Everything Nathan used to tighten up the stair railing, including the drill, screws, hammer, bungs, and touch up paint, can all be found at home centers.