How to hook up a humongous handrail

Handrail stock comes in 8', 12', and 16' lengths, but some handrails need to be several feet longer than 16'. How do you join two pieces of rail to get the length you need? The humble hanger bolt offers a handy solution. These headless fasteners have one end threaded like a lag screw, the other like a bolt. You’ll find them in various sizes at the home center or hardware store; and for exterior use, they come in stainless steel or galvanized versions. To join rails end to end, square cut your rails, making certain the joints land on or near one of the rail’s supports. Mark the center of the mating ends and drill a pilot hole sized for the screw end of the hanger bolt in one of the handrail ends. Use two locked nuts on the bolt threads to drive the screw intothe pilot hole. On the mating rail end, drill a hole for the bolt end sized about ¹⁄₈ " larger than the bolt, as shown at right. Then use a 1" spade or Forstner bit to bore an access hole in the bottom of the rail that intersects the bolt hole you just drilled. Insert the protruding hangar bolt into the bolt hole. Add a washer and thread the nut through the access hole. Finger-tighten the nut and line up the rail ends. Tighten the nut with a small wrench.
—from the WOOD® shop