A box-type, or shadow frame, essentially is a deep frame, where the back of a frame is shifted 1 - 2 cm or more behind the glass. This can be used simply to add style to the frame, or out of necessity to frame thick artworks or even artefacts or medals, which are not flat in nature.

It also offers space to place an artwork on a background mount apparently floating over it. In this case the space between the glass of the artwork is not necessarily significant, but the depth of the frame is made sufficient for the floating effect.