The "body" of the knife is just a big wishbone, basically. One fork has the blade bolted on it, the other is tensioned so it locks the blade when it's open.
Pressing down on the fork unlocks the blade. Below you can see more clearly, I hope, the lock action. In the first photo, I'm not pressing on the lock, in the second, I'm barely pressing on it, in the third, the lock is fully depressed.
O.k., look, on my camera they were rotated the right way!