Adjustable knuckles are designed to be used with the straight iron balusters in the versatile series, and work well for knee wall applications (the wall running parallel to your handrail on your stairs). The adjustable features allow you to install the knuckles onto railings with a much shorter height so that the pattern can stay consistently centered without cutting from both ends.
The knuckles are installed by tightening a set screw on the side of the knuckle.