The Baseplate.

Lower the baseplate into position and locate the rear end first - the hole in the baseplate fitting over the peg on which the rear bogie pivots.

The peg at the left hand end of the photo fits inside the elongated hole in the front bogie. Move the boie around until the baseplate drops into position. Check that the peg is located in the hole by pulling gently on the bogie.

Fasten the screws. The pastic around the screw holes is the weakest part of the baseplate - and tightening the screws is what causes it to break at that point. As soon as you feel the resistance, stop turning. It's the little extra tweak that casues the damage.