This drill is done with 4 players.
This drill helps players hit crosscourt ground strokes and down the line volleys.
On one side of the court there will be 2 players at the baseline. One on the deuce side the other on the ad side. The other side of the net there will be 2 players playing at the net. One on the deuce side and the other on the ad side.
One of the players at the baseline starts the rally cross court to one of the players at the net. The player at the net must hit the ball down the line. Continue this method, the players at the baseline hits cross court and players at the net hit down the line. Switch roles after a while so the players at the baseline get to hit some volleys and vise versa for the players at the net.
Also be sure to switch sides of the court with your partner so you can hit forehands and backhand crosscourt.