Function options vary, but are primarily Keyed Entry, Passage, Privacy or Dummy. Keyed Entry door hardware is generally installed on exterior doors where locking is necessary. Passage door hardware is typically used on hall and closet doors where you want the latch to keep the door shut but you do not need the item to lock. Privacy door hardware is usually installed on bedroom and bathroom doors where you need locking capabilities from the interior but do not need a key lock from the exterior. Dummy hardware is used on doors where a latch is not needed and is used as a decorative door pull. Dummy hardware is sold in either singles or pairs, so be sure to check the description for how it is packaged by the manufacturer.