Complex sentence: Colloquially the wagons might be referred to as "four feet gauge wagons", say, if the infrastructure had a track gauge of four feet, but this nominal value does not equate to the flange spacing as some freedom is allowed for.
Split into simpler sentences: Colloquially the wagons might be referred to as "four feet gauge wagons", say, if the infrastructure had a track gauge of four feet. This nominal value does not equate to the flange spacing as some freedom is allowed for.