Ceiling_LowerByValueTimes8
From ZDoom Wiki
199:Ceiling_LowerByValueTimes8 (tag, speed, height)
tag: Tag of affected sector speed: How quickly the ceiling moves height: Amount to lower ceiling by
Usage
Lowers a tagged sector's ceiling by (height * 8) units. 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.

