In the old days when open back banjos were the only ones around, banjo necks were held on by a central "dowel stick."
This open back banjo has a very traditional look. The body of the instrument (the "pot," "rim" or "shell") has 24 hooks and nuts holding the head tension. They pass through "shoes" that are bolted through the shell. The neck is held against the shell with a U-shaped clamp that fits around the dowel stick. Additionally, the dowel stick is screwed from the outside at its other end. Open back banjo necks are seldom adjustable, but they are very strong and generally don't need adjustment.
Modern resonator banjos have their necks held on by two coordinating rods:
These rods are used to adjust the action and keep the neck aligned. With its resonator off, you can see this banjo has a heavy "flange" through which the head tensioning hooks are bolted. This flange is extremely strong, and resonator banjos usually need them to handle the extra head tension that players demand. The higher the head tension, the louder and sharper the tone.
The resonator usually screws in place easily to allow access inside for adjustments.
Here's a banjo that's been converted for use with a resonator:
It has the individual shoes of the open back, and some decorative trim pieces or "flange plates" to make the resonator look like it belongs there. A few high grade instruments are made with individual shoes and plates, but they are unusual, and as heavily built as those with cast flanges.