Used by the routine at EB13. A location descriptor for the character's current location has been found, and it corresponds to a location that is next to a door that happens to be closed. In this case we process the remaining location descriptors for the character's x-coordinate, one of which may be specific to the character's z-coordinate (1=behind the closed door, or 2=in front of it), and thus provide the appropriate direction descriptors (which are returned in C). For an example of where this can happen, see the three descriptors in the location descriptor table at C320 that correspond to the entrance to the shop at the far left of town.