Use the patterns to cut out and trace onto tougher material such as card stock or tag board. Construction paper is practical, but less desirable for strength. Fold it in half. Place the inside edge of the helmet pattern on the folded edge of stock, trace it carefully, and cut it out. Cutting the material folded saves time and insures that the final product will be more symmetrical.
Folds add strength to the card stock just as they do to the steel of a real helmet.
Now would be a good time to punch the holes needed for assembly. Cut on solid lines. Dotted lines indicate folds. Breathing holes can be punched in the visor in even rows or creative patterns. The visor viewing slot or opening can be made larger or configured differently.