This 'primal father of helmet closures' is as simple as it is efficient and safe. It is the only approved closure for competitive use.
You slide the strap through two rings and then back through a single ring (see image 1), which causes a lock.
In this way, you clamp the helmet with every use. It cannot come off by itself. And that is precisely why the double-D ring is still widely used in helmets.
And no, don't worry: if you do it three times, you can do it forever without help.