ms, "Notice that the sector has thick lines all around. The thick lines indicate that those lines are one-sided."
SECTOR,-112, 0,-32,-80
ms, "This sector has thin lines because it is double-sided. The editor detects situations where a sector is inside another and makes it double-sided automatically."
SECTOR, 80, 64, 272,-144
ms, "You can use a void to create columns and solid walls. Insert voids with the sector tool with the second mouse button."
VOID, 144, 0, 192,-48
ms_end, "The void lines are one sided, so they are drawn thick."