This is an excerpt from Volleyball Systems & Strategies by USA Volleyball.
Block the Line and Dig Inside Strategy
Explanation of Tactic
Assuming that most of your team's opponents will prefer to hit crosscourt, the strategy to block the line and dig inside is a good choice for a team who has better diggers than blockers. Lining up the block to take away the line shot, which at most levels is not hit as often as crosscourt anyway, still provides an opportunity for the blocker to protect the shot from being hit for a kill. In essence, this strategy invites your opponent to continue hitting their favorite shot because your team knows its diggers can dig the best shot their hitters have to offer. If effective, this strategy can have a demoralizing impact on hitters, as time and time again their best shots are dug. This can also allow your line diggers to come off the line and angle slightly crosscourt as well, providing an additional digger in the area more likely to be attacked, or allow her to release forward for a possible tip or short roll shot over the block.
Teams that incorporate this strategy will have their outside blockers set the block with their outside arm just inside the antenna, giving the attacker limited opportunities to attack the line. The outside blocker should be lined up close enough to the antenna that there's not enough room between the blocker's outside hand and the antenna for the ball to fit through.
The backcourt, again working on the assumption that hitters hit crosscourt more than down the line, should "flood the zone," which means placing more than one digger in the crosscourt position (figure 11.1a-c). Notice in the figures that the left-back and middle-back diggers are in position to dig any type of crosscourt shot the hitter attempts, including the sharp shot hit from 20 to 25 feet (6-7.6 meters) deep and shots hit to the deepest part of the court.
From the middle-hitting perspective, even though middle hitters might be more confident hitting back to the defender's right-back position than outside hitters are in hitting the line shot, the middle-back and left-back diggers are still placed in the crosscourt zone. If the middle hitter begins to hit more balls to the right-back area between the right-back digger and middle digger, the flooding-the-zone tactic can still be implemented simply by moving the middle-back digger toward the right-back position rather than the left-back position. Be sure that one digger remains committed to handling any ball an attacker might hit down the line.
It's easier to use the block-the-line-and-dig-inside strategy in a two-blocker system, but it can also be used with one blocker, especially if a team's digging skills far exceed their ability to stop the opponent's attacks at the net.
This is an excerpt from Volleyball Systems & Strategies.