This has to have come up among the copious writings surrounding Cubism, but the facet – a unit of composition often used by Picasso and Braque – can resemble a sheet of paper hung on a wall.
Signature elements include a generally rectilinear shape, a highlight and a shadow side. One can imagine a wall full of notes and sketches begging to be arranged. Makes me think of Da Vinci and his cracks.
Some of you may be shaking your heads at my ignorance of the literature. If so, please bring me up to speed.