trying to site my bow in for season this year. I have heard that there is a way to mark your bow site with a make shift range finder. Use the bottom of the site and line it up on the under belly and the tick marks that you make on the side will tell you whether the deer is 20,25,30 ect yards away.

My only problem is that I do not know what the average heightof a deers torso is. Can anyone help me?