OK - in the middle of a tarp fiasco (remind me to bind up all the excess material before I sew a side to the ridgeline again!).

What are the general rules of thumb for depth of cat cut and also how do you do them? Freehand drawing? Or is there some tool here that you can run and print out a pattern?

Need a pattern for 6' and for 3 1/2'.

Thanks, FH