Railroading is a term used by stitchers to describe a specific stitching technique. When using this techniques, the floss is smoothed down with a laying tool or tapestry needles and floss strands lay side-by-side - like the rails of a railroad track. In the image above, the half stitch
on the left has not been smoothed. The stitch on the right was smoothed with a tapestry needle. The twist of the floss in the left stitch is evident. The strands are not flat against the fabric.