underdrawing

A sketch done on the ground of a work of art before paint, pastel, ink, or other more permanent medium is applied.

Depending on the medium used, underdrawing in embroidery and other decorative techniques may be revealed by radiography where it is relatively radio-absorbent in comparison to other materials used either in the original artefact or in later mounting and conservation methods.

When subjected to printing or photocopying, the blue underdrawing will disappear, leaving only the ink lines.

An image of a figure that is slid under the page on which a designer draws a garment, so that the result conforms to the figure's proportions.

You can use a croquis as an underdrawing for fashion drawing

Used as a base or underdrawing, it can be slipped under a page in the sketchbook and worked off of from there.

An underdrawn cover or lining of the underside of a floor or roof with plasterwork, boarding, or similar.

He has the whole of the room underdrawn, with the exception of two bays at one end; he admits plenty of air by the windows in the roof into the triangular shaped space formed by the roof and the underdrawing; it is here deprived of its moisture, and passes into the spinning room, where the underdrawing stops short of the length of the room.

Tongued and grooved boards ⅝ in. thick form the underdrawing for the roof.