what is the difference between a pen knife and a pocket knife
Penknife Today the word penknife is the common British English term for both a pocketknife, which can have single or multiple blades, and for multi-tools, with additional tools incorporated into the design.[2]
Key (lock) A key is a device that is used to operate a lock (such as to lock or unlock it). A typical key is a small piece of metal consisting of two parts: the bit or blade, which slides into the keyway of the lock and distinguishes between different keys, and the bow, which is left protruding so that torque can be applied by the user. A key is usually intended to operate one specific lock or a small number of locks that are keyed alike, so each lock requires a unique key. The key serves as a security token for access to the locked area; only persons having the correct key can open the lock and gain access. Common metals include brass, plated brass, nickel silver, and steel.