The Schnibble pattern for June's parade is Dulcinea. There are four sections to be trimmed down before sewing them together to make the pinwheel block. The above photo shows you how the pattern directions guide you to trim to 3.5" unfinished.
I'm thankful I have this ruler to get the same results. I'm even more thankful I remembered I had it because this is a much easier way for me. Just thought I'd share.