Ampere turn diagram

Hello Guys
I've been looking at some old engineering documents that relate to the
calculation of transformer reactance, it goes on to explain the use of
ampere turn diagrams as an aid to reactance calculations.
Now I've related the trapeziums to coil dimensions - but I was trying
to understand how these trapeziums are constructed with more complex
winding arrangements.
Are there any engineers here who are willing and can explain how to
construct the ampere turn diagram from the coil dimensions.
TIA
Euclid
( please remove spambin to reply)