Correct deck railing angles are vital to ensure the safety of individuals using the deck stairs. When the angle of the railing does not match the angle of the steps, people using the stairs will lose their balance and perhaps fall down the stairs and receive severe injuries. Matching the angle of the railing to the stairs requires precise measurements with common carpentry tools.
Set the short -- 16-inch -- leg of a framing square across two steps near a 4-inch by 4-inch railing support post. Slide the framing square until the top of the long -- 24-inch leg -- sits 4 inches past the support post. Secure the framing square to the post with a self-locking C-clamp.
Place a 4-foot level on top of the secured framing square. Slide the level until it crosses the inside face of the support post.
Drag a pencil along the bottom edge of the level. Remove the level from the support post. Release the self-locking C-clamp. Set the framing square aside.
Measure the distance from the top of the nearest step to both the low and high point of the pencil line to determine the angle of the rail support.
Divide the angle measurement by 2 to determine the angle needed between the upper railing connections.