In art, the term 'key' is used in a variety of context. When referred in the context of molds, it is an interlocking device in the joint of a mold. It helps in correctly reassembling the mold. In architecture, the term simply refers to the keystone at the apex of an arch.  The term key may also be used to refer to the roughening of a surface in order to enable paint to adhere more effectively to the surface. Again, the key symbol when used in paintings denotes different meaning based on the era, the painter, and the country in which the painting is done.

In addition, the term is also used to refer to the wedges that are driven or fastened into the interlocking corners of stretcher bars (made of wood) to generate tension on canvas support.