I don't know how you do it. I just made 3 ends to replace the plain-jane ends I have in just one of my OK Engines LW passenger cars. All I had to do was cut (3) pieces for the ends (interior and exterior walls), (4) 1/16" sq pieces, (2) pieces for the diaphragm mounts, and (2) doors, plus cut out (3) windows. All this was 1/16" thick styrene and my fingertips are killing me! I still have 2 cars to go