The screen is carefully removed with a razor saw, and a replacement window frame cut from plasticard.
The roller is made from aluminium tube, with end caps made from plasticard, and the springs are left over elevation springs from Tamiya kits. The whole thing is just for show, there is no movement in it what so ever.
Rear wheels on the scout car are from another M16 - in the past some vendors would break up defective M16's and part them out, thoI haven't seen this done now for several years.