Obtain a post card of the Big Boy model.  An image, for printing, is available at the bottom of the page.

Cut all four parts of the Big Boy out of the postcard.  You may use scissors, I prefer an x-acto knife and a cutting board.

Fold the parts along the dotted line.  Be careful to make a straight fold.  As seen here i use a straight edge to carefully fold the part.

Here are all the parts, folded, and ready to be glued.

Glue the top parts together.  The two parts that have the top of the fuselage should be glued together first. Together, they will look something like the image here.

Glue one of the bottom pieces to the top piece assembly. Be sure to line up the tail section and the nose, the wing should automatically come together.

Glue the final piece to the assembly. Again, make sure the tail and the nose are lined up, the rest should come together naturally.