US Patent 7748686 Railing ball

A deck and stair railing has top and bottom rails joined to upright posts and upright tubes extended between the rails. Ball knobs mounted on plates or the rails are secured with deck screws to the rails to retain the tubes in assembled relation with the rails. The ball knobs have continuous circumferential ribs located in force fit relation with inside surfaces of the tubes. The tubes have projections that engage the ball knobs to prevent the tubes from rotating relative to the ball knobs.