The whole point of a clamp pliers, sometimes called a vise, is to lock the pliers in the closed position. YiYiTools locking pliers cannot handle this simplest task. The pliers stay securely locked if you hold them in the absolute maximum position where the jaws actually touch. If you open the jaws, the lock will start to break more easily. A good 1/8 inch of pressure was enough, and at less than 1/2 inch, a simple finger press on the top would pop the whole thing open. This thing even came open