All points must be co-planar, or triangulated surfaces will result. Making a flat face on the sloped portion of the wedge below. The boundary curves can be lines, arcs, circles, plines, or even a point. Making a meshed surface between the two curves as shown below. Creates a meshed surface that is a blend of 4 boundary edges.
Boundary edges can be lines, arcs, plines or splines.
Endpoints of all 4 boundary edges MUST touch.