The head of virtually all banjos is held in place by a "tension hoop" which is a brass (usually nickel plated) ring that's gripped by 24 hooks:
This is the most standard style, where the tension hoop is notched to accept the hooks to keep them neatly aligned. These hooks are very strong and securely mounted. They need to be to tighten the head and hold it tight for decades!
This tension hoop is grooved through its length and the hooks fit right into the groove:
It's just as secure as the notched hoop as long as the hooks are strong and well made. The grooved hoop was more common on older instruments, because it will accommodate a variety of hook positions and arrangements.
Here's an unusual high grade banjo:
Its hooks are not hooks at all but are really bolts that pass through a heavy cast tension hoop and thread directly into a heavy flange. This is the famous "top tension" style Gibson Mastertone introduced in the late 1930s. The idea is that you can tighten the head without removing the resonator. Immensely strong, but expensive to make, this style is really not in use today, except as reproductions of the vintage Gibsons. (There were other much less desirable top tension instruments made by a variety of makers.)
Here's something to watch out for!
This banjo was made in Korea, so it's a beginner model. Notice the hooks:
They're wide and flat, and they hold a tension hoop that's way below standard width and strength. But the hooks are the real problem.
These imported hooks are so weak that if you tighten them very much they straighten right out and drop off. Look at this one, it's just about to fail:
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