SECTORS 1 : ceiling/floor 120/0 2 : ceiling/floor 128/128; 3 : ceiling/floor 128/128; 4 : ceiling/floor 0/0

LINEDEFS a : trigger 91 to sector 2; b : trigger 91 to sector 3

Again this trick relies on the 'trigger 91' effect of instantly lowering the floor with a "raise to minimum adjacent ceiling" while this ceiling is in fact at ground level. Sector 2, 3 and part of the solid wall make up the 'door' in various stages of opening. Sector 2 and 3 are split into two parts, one making up the actual door, the other a dummy sector linked to a sector with its ceiling at ground level.

Lots of variations are possible, including sliding doors. All nodesbuilders are capable duplicating this effect. Have fun :)