The quarterback generally either starts a few paces behind the line of scrimmage or drops back a few paces after the ball is snapped. This places him in an area called the "pocket", which is a protective region formed by the offensive blockers up front and between the tackles on each side. A quarterback who runs out of this pocket is said to be scrambling. Under NFL and NCAA rules, once the quarterback moves out of the pocket the ball may be legally thrown away to prevent a sack. NFHS (high school) rules do not allow for a passer to intentionally throw an incomplete forward pass to save loss of yardage or conserve time, except for a spike to conserve time after a hand-to-hand snap. If he throws the ball away while still in the pocket then a foul called "intentional grounding" is assessed. In Canadian football the passer must simply throw the ball across the line of scrimmage—whether he is inside or outside of the "pocket"—to avoid the foul of "intentionally grounding".