if( !str_cmp( arg, "ex_flags" ) )
argument = one_argument( argument, arg2 );
value = get_exflag( arg2 );
if( value < 0 )
send_to_char( "Bad exit flag. \r\n", ch );
if( ( xit = get_exit( location, edir ) ) == NULL )
snprintf( buf, MAX_STRING_LENGTH, "exit %c 1", dir );
do_redit( ch, buf );
xit = get_exit( location, edir );
TOGGLE_BIT( xit->exit_info, 1 << value );
This lovely bit of code is in do_redit, build.c, and from what I can tell is abandoned. It's not revealed in the syntax message or in the help for redit. It appears the intent was to take a single exit flag, and apply it to the specified exit, creating that exit if it doesn't already exist. But careful examination shows it never asks for the direction of this exit, and so it just assumes north in all cases. If there is no north exit in the room, it'll crash the program.
My feeling is this code was not intended to remain in use since it's not documented. So abuse carefully. I'd recommend removing it if you find it.