CC-BY-SA-3.0
Taken from cmss13-pve at https://github.com/cmss13-devs/cmss13-pve/blob/0afcb527e30cb9d24151005c28f095d704b24c83/icons/turf/walls/upp_grey.dmi; CMU 3D source-corner crops and isolated composition. See SOURCES_SPP_WALL.md.
