Fillet (picture framing)

[2] The picture framing term is probably related to, though not necessarily derived from, the engineering term, which it is frequently pronounced similarly to; however, unlike the use of fillets in mechanical engineering, the use of "fillets" in picture frames is wholly decorative.

Fillets are typically made of soft or hard wood, and feature a flat "lip" which can fit underneath a mat; the non-lip portion is what is displayed.

Except for their shape and size (which is understandably small), fillets are constructed similarly to picture frames, usually from wood or polystyrene.

[3] However, one can also use inverted fillets as form of picture frame on small, flat objects, as seen below: In this case, the card was glued to the lip of the inverted fillet (which is thus hidden behind the back of the card).

It is important to note that only very small, extremely flat objects can be framed using only an inverted fillet, as a fillet lacks the depth of a traditional picture frame, and due to its size, weight and construction, could not support a great amount of weight on its own.