A member or panel of the layout, in the curtain wall's frame (metres): u along the path, v up.
Mullion centre lines (u), each full height.
Panels: the clear openings between member faces.
Transoms: centre height v, spanning u0 -> u1 between mullion faces.
U grid lines, 0 and the length included.
V grid lines, 0 and the height included.
A member or panel of the layout, in the curtain wall's frame (metres): u along the path, v up.