I'm just starting out with SRB2 level design, and I'm trying to divide a sector into two vertically stacked rooms with an FOF in the center. I know how to create a standard FOF, but I'm having trouble preventing the FOF sector's linedefs from merging with the room sector. Is it possible to make the FOF stretch wall-to-wall without any gaps, or will I have to make a gap along at least one edge?