I designed these for FDM printing; they are simple files; the ones shown in the photos were printed at .2 mm layers.
Sewer Access Markers for 28mm Gaming
This file contains the .stls to print markers (both round and square) to indicate Sewer access points (formerly referred to “manholes” by those of us from a previous age). Bolt Action has sewer rules in the Road to Berlin campaign book, and no doubt will have more coming out in the Stalingrad book. These markers can be used to indicate locations on the table from which troops emerge.
They are an original file, and should be usable in other game systems.
(Downloads - 161)