One team of two players stands at the net (about halfway between the service line and net), and another team of two players is at the baseline on the other side (see graphic below).
The coach (who stands close to the net post) will always feed the ball to the team at the baseline.
They play the point out.
If the team at the net wins, they receive a point and keep playing at the net. When they lose, they move back to the baseline.
If the team at the baseline wins, they don’t receive a point but they do move up to the net (where the points count) and play against the opposing team, now at the baseline.
So teams score only when they win by playing at the net.
The transition from the net to the baseline should be done in 3 seconds (counted by the coach).
The first team to 7 points wins, and then they switch sides.
Note:
This is a players' favorite doubles drill because it gives them a good workout (moving back and forth), improves their net skills, and it is fun. :)