Dec 10, 2015 - Then I covered the carbon paper with three sheets of copier paper and traced the rails. This made a "positive" trackwork template when looked at from above. But I'll be building the bridge upside down. The bridge will be deck girder construction made from two 85' sections and one 50' section. The 50' section has girders that are not nearly as tall as the 85' sections. So upside down construction is required to keep the top surface of the bridge flat.