Score the fold lines on the body of the train car, including the folds indicated at the ends of the sides. Cut out the body of the train. Fold the sides sharply at the top and just slightly in the middle of the sides to give the sides a slight outward bulge. Roll the roof of the train against a round pencil or dowel to give it a slight curve.
Score and cut out the underside of the train. Fold the tabs back and glue inside the sides of the train one side at a time. Match the underside to the lower fold of the train side, and the top of the tab to the upper fold of the train side.