WHEN I WAS FIRST UNSURE OF MY RANGING ABILITY IN MY HEAD, I WOULD TAKE A MEASURING WHEEL ADN MEASURE IN EVERY DIRECTION THAT I COULD POSSIBLY SHOOT FROM MY TREE. THEN AT LIKE 20-30-40-50 YDS I WOULD PUT TAKE A STICK AND STICK IT IN THE GROUND GIVING MYSELF A WAYPOINT TO LOOK AT FROM THE TREE. I HAVE ALSO SEEN GUYS USE SPRAYPAINT AND MARK THEIR YARDAGE. BUT THIS IS ALL FOR HUNTING. FOR 3-D YOU NEED TO PRACTICE PRACTICE THEN PRACTICE SOME MORE