A notch keeps the plunger in the retracted position.
5-C-NI Indexing Plunger GN 817 indexing plungers with lock-out (Type C / CK) are used for applications where the plunger pin needs to stay in its retracted position. This indexing plunger has the unique feature of the pull knob partially enclosing the top of the plunger body, allowing less debris to enter into the mechanism.