This activity sounds like a great warm-up or drill for your volleyball players. All the players start on one side of a line, once they bump the ball to another player, they cross the line and wait. The goal is to bump the ball to players on one side of the line and not have it hit the floor. The last player may bump the ball over the line where it all begins again. It's not actually as complicated as it might sound, and the players will focus more on practicing their passing. By setting a goal, or making this a competition, players will tend to work harder at making good passes.