#Thicken

Click a face, set the thickness at the geometry (the sign chooses the side), press Enter. The face grows a plate of the given thickness; the part stays one body.

#How it differs from a shell

A shell hollows out an existing body. Thicken takes a surface and grows material along it — over the whole face at once, following its shape, curved faces included.

#Where it is used

• To grow a gasket or a cover plate along a face of a complex shape.
• To make a skin along a contour.
• To add a local boss under a thread or a fastener.

#A surface instead of a part

Click a sheet (a patch, a copied face) and the whole surface is thickened at once, giving an ordinary solid. There is nothing to glue it to: the sheet is the future plate, so the source is absorbed rather than left alongside.

This is how the design layer returns to the timeline: patch, thicken, combine. A surface can be neither combined with a part nor printed; a solid can.

#The sign of the thickness

Plus and minus choose which side of the face the material grows to. Zero makes no sense.