Remove the top plate of the knee wall with a pry bar. Use a sledgehammer to remove the drywall from both sides of the knee wall. This allows access to the frame, which makes removing the wall a simpler process.
Check the frame to determine whether it is attached to the subfloor with screws or nails. If it is attached with screws, remove the screws with an electric screwdriver. If the frame is attached with nails, pry up the bottom plate with a pry bar.
Unscrew or pry the end stud attached to the adjacent wall to complete the removal of the knee wall.
Place the banister on the subfloor and against the adjacent wall. Drill pilot holes through the bottom plate of the banister and into the subfloor at 4-inch intervals with a drill. Insert and tighten 4-inch wood screws through the pilot holes to secure the banister to the subfloor.
Place an L-shaped metal bracket under the top plate of the banister and against the adjoining wall. Drill pilot holes through the screw holes of the bracket and insert wood screws into the pilot holes to secure the top plate to the wall. Repeat this process for the bottom plate.