Curious carpet

I've seen such things before, but read about it only. Concrete floors and corridors of the casemates were covered with special mats, made of thick ropes. So the gunners, dressed in boots could not accidentally make sparks stepped on concrete floor with their boots. Because of one little spark here was enough for the flight to 6-7 km. height above sea level. The carped remained here probably from the 1900's.