#Patch

Spans a surface across the picked edges. This is the first design-layer shape that was not on the body before: copying a face only repeats what exists, while a patch closes an opening.

#How

1. Press Patch.
2. Click the edges that define the boundary — at least two. Edges highlight as they do in Fillet; clicking a face takes all of its edges at once.
3. Enter — the surface appears; Esc — cancel.

#Worth knowing

• Smooth or by position. A switch in the top bar. "By position" simply butts the surface against the edges — the seam shows both to the eye and to the hand. "Smooth" brings it in tangent to the neighbouring faces, leaving no seam: this is how fairings, housing transitions and rounded blends are made. An edge has two neighbouring faces and tangency goes to one of them — the LARGER one is taken: what should continue is the surface that defines the shape, not a narrow rim strip.
• The body stays as it was. The patch lives beside it as a separate surface. To make it part of the part, use Replace face.
• The boundary is stored as a description. If the edges were chosen through "expand selection" (right-click), the patch remembers the rule rather than the numbers, and rebuilds when the base changes.
• Edges need not close into a loop. An open chain works too: a piece of a dome over three edges is an everyday case.
• If it will not span, you get an honest refusal. The node turns red and says so; no surface is invented.