Here are a couple of fittings for a banjo with stick through the shell construction. The one on the left would wedge in a slot in the stick up against the shell, pushing the shell against the neck. On the right is the fitting for the other end of the stick. The L-shaped piece (upside-down in the photo) screws to the stick an slides up and down around the endbolt to adjust the neck angle.

Here is a neck angle adjuster on an old, simple open back banjo. Some Weymann banjos had this feature, but the one here looks like it might have been made by the owner of the instrument.

A customer brought in a Vega banjo for some work. It had a Grover Tone Ring. This attachment presses against the top opposite a small plate set against the stick.