To block out effectively, stay low, keep your feet wide apart, back straight up, and your arms straight out to the side while your hands are up (and just out from the ears).
There are certain advantages to using this position. By being low and wide, you stay tough and are hard to move even by a stronger player. Also, you force the man behind you to jump when you do, or after you do, since jumping for the ball first certainly looks like he is fouling by going over your back.
By keeping your back straight, it is obvious to the referee that he, not you, is fouling. If you bend at the waist as many players do, it often looks as though you have moved under the man behind you and therefore the foul can be called on you. This is especially important if you are the one initiating contact. If you move to the man with your back straight up, the contact will be incidental and not be called. But if you move toward the man with your back bent forward, a bit of forward momentum will carry him over your back, and it will look as though you are guilty of the infraction.
By having your arms out to the sides, you can feel the man on your back with your triceps and you can hold him out without getting a foul called on you—as long as the referee can see your hands in the air.
This is one way of blocking out. It is not the only way, but if you are not given any specific method, this one will serve you well.
Stay low, feet wide apart, back straight, arms out, hands up
The most important point of blocking out is not related to the hands, the arms, the back, the knees or the feet.
The crucial factor in blocking out pertains to the position of the head. The head must want to block out. The head must want to get in someone’s way. The head must, as a matter of habit, enjoy getting in someone’s way every time a shot goes up.
In drills, it is very difficult to block out well. Offensive rebounders have an assortment of clever spins and fakes and turns that are hard to handle. However, in games, these are hardly ever used. Hardly ever. Almost never. Or so seldom they don’t even need to be considered. In games, what needs to be considered is attempting to block someone off the board every time. If you attempt to block someone off, most likely you will because in games there is rarely much time or effort put into faking and jockeying for position. The huge majority of offensive rebounders do nothing at all; the good ones go straight for the ball with no fakes and no effort to spin once they are cut off, and there are one or two guys in the world who hit and spin and fake and change direction—and these guys are superstars.
Go back and read how many superstars there are in offensive rebounding. One or two in the world and maybe a little guard somewhere that no one knows about because he’s too small to get the ball even though he often gets to it. The point is, there aren’t many “hitters and spinners” that you need to worry about. Your primary concern needs to be with getting into the every-time habit of attempting to block out. Why?
When you review game film after game film, regardless of the level of play, you find that the majority of offensive rebounds are gotten not by clever “hitters and spinners” but by players who simply move to the ball without anyone ever getting in their way and without anyone having made any attempt to get in their way.
Technique is not crucial. Do it the way your coach tells you, or if he says nothing, do it the way it is done in the line drawing. But do it. Do you understand? Do it.
The times you let your man get an offensive rebound will very seldom be when he outfakes you. Usually, his rebounds will come when you simply forget to block him at all.
From Dick’s book Stuff