In basic terms, a liner lock uses part of the internal metal liners of the knife (the metal that "cradles" the blade when closed) to form a spring that blocks the pivot so the blade (hopefully) doesn't close until the liner is pushed out of the way. There are a lot of other methods of keeping the blade from easily closing under pressure, but they are pretty much all subject to failure if lint, dirt, and other crud get in the way of the lock and prevent it from acting as a wedge.
Cleaning the knife by using swabs, "canned air," tooth picks, etc., helps keep this at bay. Since most folders live in pockets, they collect crud. An easy tip for keeping the crud to a minimum is to turn your pockets inside out when you throw your clothes in the wash.
If you turn your pockets inside out right now, I'll betcha there's a pretty good collection of lint. I still don't know how it gets from the pocket to the belly button, though. This might require further study. Maybe I'll go find a federal grant to fund some young ladies from the local college so I can study their navels. This might envolve intensive research.
Just consider the things I'll suffer through for the betterment of science... Your tax dollars should be hard at work!
