Ortho Close and Close are command-line options that let you efficiently create a closed space when you add walls.
Ortho Close
This option closes the space by drawing 2 walls based on the direction you specify. The direction is extended until it meets a line perpendicular to the initial edge of either the wall. You enter or (Ortho) at the command line to use this option when placing walls.
Closing walls with Ortho Close
Close
This option closes the wall by creating a wall segment from the last point specified for the walls to the first point specified in this group of walls. You enter c (Close) at the command line to use this option when placing walls.