The three types of blade locks are lock back, frame lock, and liner lock. The first one is one of the earliest designs. There is a little notch in the handle along the spine of the knife, where your thumb is used to depress the locking system. This does not suit one-hand operation. On a frame-lock knife, one side of its frame slides under the blade, allowing the blade to fully deploy. This gold-standard locking system optimizes the security and one-hand operation. Liner lock shares the same mechanism with frame lock, but instead of sliding a whole side of the frame into place, one side of the liner shifts and locks the blade, leaving the rest of the handle to stay in place. This locking system is common on modern knives, and it is secure and functional, yet cheaper to produce than the frame-lock system.