Its purpose is to stop secondary defenders from taking a position under the basket in an attempt to draw the offensive foul when a player is driving to the basket . If an offensive player drive past his primary defender on the way to the basket and a secondary defender come over , he must establish a legal position outside the RA to draw an offensive foul . If the drive start inside the Lower Defensive Box ( LDB – this is the area from the bottom tip of the free throw circle to the end line between the two 3 ’ posted @-@ up marks ) , the secondary defender is legally allowed to be positioned inside the RA . The restricted area also do not apply if the secondary defender jump in attempting to block the shot , the offensive player lead with his leg or knee in an unnatural motion or use his off arm to prevent the defender from blocking his shot . The RA do not extend from below the backboard to the baseline . Therefore , if a player drive the baseline and is not attempting to go directly to the rim , the RA do not apply .