A bow pen also known as a ruling pen was designed in the early 1900’s for draftsmen for drawing straight lines of...
OO9 is 4mm to the foot scale (that is OO or 1/76) but using 9mm track gauge (the same size as N gauge). This is narrow gauge modelling and is meant to represent 2ft gauge in real life. The name comes from OO scale and 9mm track. It is a very...
 