A channel block is a block that funnels the ball toward a specific defender. The blocker leaves one angle open intentionally. Therefore, coordination matters.
Beginners may think blocks must close everything. During a rally, the blocker takes away the line. The cross-court remains open by design. A defender waits there. The hitter swings cross-court. The defender digs the ball cleanly.
The block and defense work together. Channel blocks reduce court size. They simplify defensive reads. Teams using them defend smarter, not harder.