Kirkwood, Missouri. March 6, 2005.
These are stay bolts on a steam locomotive on display at the St. Louis Museum of Transport. Stay bolts are used to reinforce the inner and outer flat metal sheets of the locomotive's boiler. Due to the high amount of pressure inside the boiler, the flat sheets would loose their flatness without the stay bolts which would probably lead to the boiler failing in a bad way.
Photo © Tom Gatermann.