Like the name of the drill says, the objective of this drill is to improve the players change of direction.
Each player starts in the center of one of the service boxes. It can be done with Rackets or without them (which will be harder for the players).
The coach sets a timer (i.e. 30seconds). On his command, the players start changing direction by sidestepping left and right (always facing the opponents side), touching the lines with their racket (easier), or with their hands (harder). Once the 30seconds are over, the players get a 10 second rest, then prepare for the second round. The second time only do it for 20 seconds, and the third for 10 seconds.
For players with higher stamina level you can do 60, 40 and then 20 seconds.
Or you can make a race to see which player reaches the given target first (i.e. 40 line touches).