Exterior wall. From Okrand, startrek.klingon, 12/7/98.An exterior wall (that is, a wall which separates the inside of a building from the outside) is a reD. Opposite of pa' reD, tlhoy'.

Use reD “exterior wall” for an object’s surface that’s not the top or bottom or front or back. That is, the use of reD need not be restricted to structures. If you need to be more specific, you can add in poS "left (side)" or nIH "right (side)."

Also used to number the sides of a geometrical object as in:
quadrilateral - loS reD mey'
pentagon - vagh reD mey'
four-sided base - loS reD 'Impey'
five-sided base - vagh reD 'Impey'