It could be part of a jig for building carriages, so you can accurately locate the wheels and axles as your start point. I used to deliver milk to the carriage works in York and there were loads of wheels and axles waiting to be used, but I was always there early and never managed to get in side the workshop
Was that the coach works at Holgate on the A59?
Am in and out of there quite often loading axle sets, and it's a fascinating place to wander round.