On almost any properly made hardwood basketball floor, a single nail is pounded into the very center of the free throw line, directly in front of the center of the rim. The nail should be on the outside of the free throw line and usually painted over. It can be difficult to see or find on some courts at times, but it should be there. Apparently this nail was originally put there by the painters to center the court and to line everything else up.
Line your body up for a free throw by centering yourself using the nail on the free throw line
When shooting a free throw, you should center your shooting arm over that nail. If your shooting arm is properly lined up like a catapult that is directly perpendicular to the rim, then the ball should go straight forward on launch, while using your guide hand to just keep the ball steady.
Many coaches will suggest to place your right toe (if you’re right-handed) over the nail, but we feel that only makes sense if you are launching the ball off your right shoulder. Rather, we suggest to put the nail some distance right of center between your two feet. A right-handed shooter should toe the line with his right foot. How far you put your left foot behind the line should be left to what feels most comfortable for you. Most people have their left foot toe back about half of your right foot.
The most important part is to line yourself up consistently the same way. Your feet should be in the same position for every single free throw you ever take. It’s the easiest part of a free throw to keep consistent, so make sure you do it right.