Semi...may I tell you to throw away the parallel rules and plodding over to the compass rose AND most course line drawing. There is a $15 miracle called the Weems and Plath Course protractor that will allow you to plot a course (magnetic or true) between any two points in less than 10 seconds. Buy it and you will shower me with praise!! (G) I did all my navigation chart work in the cockpit in seconds and never used a parallel rule in 6 years of cruising. Next to the miracle cloth this is the holy grail of under $20 must have boat items!! This and some dividers are all you need.
For those of you who I've made curious...here's the one page "operators manual".