A liner lock has a leaf cut out of the handle's liner. When the blade is fully open, the leaf springs open and blocks the back of the blade, preventing it from closing. Since the liner locks has no spring pushing against the blade, it has an incredibly smooth action. To unlock the knife you thumb the leaf out of the way, obviously using just one hand. The blade has a detent in it, and a small ball bearing embedded in the leaf drops into the detent when the blade is fully closed, keeping the knife from opening accidentally. This lock format is extremely strong when done correctly.