Popular folding knife locking mechanisms include:
Slip-Joint - Found most commonly on traditional pocket knives, the opened blade does not actually lock in a solid position but is held in place by a spring device that allows the blade to fold if a certain amount of pressure is applied.
Lockback - A "Lockback" is a type of folding knife that locks open. Locking folders provide much of the confidence of a fixed-blade while open, yet enable you to fold the blade for safety and carrying convenience. A Lockback gets its name from a rocking lock plate visible on the back of the handle. Opening the blade causes the "rocker" to lock against the blade so it locks open. Pushing down on the rocker at the back of the handle releases it and enables you to close the blade. Lockbacks require two- hand closing, though some are one-hand openers.
Liner Lock - The “Liner Lock” is one of the most common today on knives, especially so-called "tactical" folders. Its main advantage is that it allows one to disengage the lock with one hand. It con sists of a liner bent so that when the blade opens, the liner presses against the rear of the tang, prevent ing it from swinging back. To disengage, you press the liner to the side of the knife from where it is
attached to the inside of the scales.
Frame Lock - A "Frame Lock" operates like a liner lock, only the lock is a tensioned part of the handle frame with an open channel. When the blade opens, the frame lock moves into the handle opening and locks against the blade. Pushing to the left releases it from its "locked" position so you can close the blade.
Choosing what lock type is best will be determined by your preference, as well as the type of work you plan to do. For example, if you want to be able to operate the knife with one hand, you will probably not want a Slip-Joint or Lockback. A Liner Lock or Frame Lock will be the better choice.