Trim refers to the design and function of the visible portion of a mounted lock. There may be several trim options to a particular lock. Options may include the finish (such as brass, satin nickel, dark bronze, etc.), function (such as entry, storeroom, privacy, etc.), number of cylinders, knob or lever, and more. In some cases, especially with mortise locks and patio door locks, the trim is, or can be, purchased separately from the actual lock body. With exit hardware, you may choose no exterior rim at all if the door is meant to be used as an exit-only door