This is 'Flow Chart of Sexual Decision making', according to medieval penitential manuals. I got it from a post by Boingboing guest Blogger Maggie Koerth-Baker. If you go through the chart, you find it pretty hard not to 'sin' by a sexual act. Even if you can hardcode the procedure into your subconsciousness, you lose all appetite for sex after it. This is IMHO, precisely what the chart is meant for.