This figure shows the two-dimensional faces of two abutting three-dimensional unstructured hexahedral grid cells. The donor cell face is drawn using solid lines, and is labeled as "HEXA_8 volume element #238". Its corners are labeled "node 1", "node 2", "node 3", and "node 4". The receiving cell face is drawn using dashed lines, with one corner labeled "R" inside the donor cell face. Arrows are drawn showing that the location of point "R" in the donor zone is "0.75 in the 1-2 direction" and "0.55 in the 1-4 direction".