I'm in the process of using some type of tape around bow sight with black marks for different yardages. If you know your average deer is 18 inches from backbone to brist then you should be able to tune/measure your ink marks on tape in your backyard. Just work with a piece of cardboard that is exactly 18 inches tall. Mark top and bottom locations on tape for different yardages. No need for an expensive rangefinder and no need to dig in your pocket and try and find it during a critical time right before the shot. Make sense?