seems to have forgotten
the Trapper Keeper's nifty
3-Ring open/close mechanism
Typical 3-Ring binders had two tabs at the top and bottom of the backbone that when flipped in opposing directions, the rings would snap open.
Not the Trapper Keeper.
The Trapper Keeper had a nifty little slide bar at the bottom of the backbone. When this slide bar was pulled down, half of the spine would slide away from the other half, pulling the rings apart. You'd load it up with looseleaf paper, and push the slide bar back in. It would lock with a soft click, and you were good to go.
Of course, this mechanism was prone to break, but the geeks in the crowd always managed to somehow repair it. (I impressed many a girl in my elementary school days with my slick trapper-keeper-3-ring-repair-technique.)