Ceiling_LowerToLowest
From ZDoom Wiki
253:Ceiling_LowerToLowest (tag, speed)
tag: Tag of affected sector speed: How quickly the ceiling moves
Usage
Lowers a ceiling to the height of the lowest surrounding ceiling. If the ceiling is at a position lower than the lowest surrounding ceiling, it will instantly rise to the level of the that ceiling. If tag is 0, then the sector on the line's back side is used.
Examples
As the ceiling specials are fairly trivial, examples of every one can be found in the example wad, Squash. This wad runs on Map01 of Doom2.

