Things You'll Need
Power drill and hole saw
A stairway serves as a safety hazard if it is open on one or both sides between the stairs. Enclose an open rail by installing iron spindles, or balusters, along its underside. The lower ends of the spindles are anchored securely into predrilled holes through the stair treads. When properly spaced and attached, the iron spindles also add an elegant touch to the space, create a striking contrast against the wood railing and give the stairway a finished look.
Measure the length of the rail between posts. Subtract the maximum gap size between spindles according to your local codes, which is usually 4 inches, from the rail length. Divide the result by the sum of the rail length and spindle width, and round off the result to the nearest whole number to determine the number of spindles you need to install along the rail.
Cut two scrap pieces of lumber down to 4 inches (the spacing between adjacent spindles) and 1/2 inch (the width of the spindle).
Mark the locations of the spindles on the rail. Place the 1/2-inch-width spacer flush against the underside of the rail, and mark its outline using a marker. Place the 4-inch spacer next to the mark and mark its other end on the underside of the rail. Set the 1/2-inch spacer next to the mark and mark its outlines. Continue this process of marking the locations of the spindles on the rail. Typically, you need two to four spindles per tread.
Extend a carpenter's level from the spindle locations on the underside of the rail to the corresponding treads. Mark the locations of the spindles on the treads with a marker. Ensure the level reads plumb before forming the marks.
Using a power drill and a hole saw, drill a 3/4-inch-deep hole into the treads at each spindle's marked location. Also drill 1 1/2-inch-deep holes into the underside of the railing at each marked location.
Measure the distance between each tread and the underside of the rail. Cut the iron spindles 2 1/4 inches longer than the measurement to accommodate the depth of the holes with a jigsaw and metal cutting blade.
Slide one end of a spindle into the hole in the rail, and insert its lower end into the hole in the tread. Apply a length of masking tape to the upper end of the spindle to prevent the epoxy from dripping downward. Repeat this process of installing spindles along the stairway.
Squirt epoxy into the holes in the treads and undersides of the rail. Allow the glue to dry before you remove the tape.
If desired, substitute iron spindles with wood spindles.