 The plates were three feet long, L-shaped and made of cast iron, weighing 40 lb.They were supported on stone sleepers weighing 60-70 lb; the ends of the plates were held down by nails driven into wooden plugs inserted into holes in the sleepers.The gauge is generally quoted as being about 3 feet 9 inches, although some recent archeological investigations suggest it may have been as narrow as 3 feet 6 inches.