No info about availability.
A blind panel with an HP ruler
4hp/4te panel and ruler. To be used for HP measurement, DIY modules, and as a safety fill in to a case.
http://www.ctrl-mod.com/product-p/control-4hp-ruler.htm
These merchants probably sell this module. Huh?
Included in 78 Racks, 35 are public:
Control Full Size HP Ruler, Screw Gauge
Abyss Devices Eurorack HP Ruler and 1U
Control 4HP Ruler Blank