I have written (free) online stair and roof calculators you may find useful.
They draw a plan of the stairs and roof, so you can see the layout
There is also a dovetail template generator herehttp://www.blocklayer.com/Woodjoints/DovetailEng.aspx
Enter the dimensions of the wood, and tail setout and it draws the template, ready to print, fold over end of wood and cut through
I've seen these posted on another forum.(rec.woodworking?) They are pretty good reference guides.
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