I'm currently building up the MDC outside frame 2-8-0 and have gotten to the part where you add the brass side rods. The instructions show that you use these little 'botton-like nuts to hold the rods on. How do you fasten the nuts on? Press-fit? glue? (what kind?) any help would be appriciated. Also does anyone have a spare gear retainer for the engine? I'm missing mine.