First, the base: used with tennis balls with ropes, can hold water/sand/mud, and is light and durable. It can be filled with sand and added with falling objects of different substances, which varies from person to person and depends on strength. It is not recommended to practice vigorously.

Second, the use steps

First of all, find an empty and flat venue; Fill the base with water/sand/soil and put it directly on the ground.

Then tie the other end of the tennis ball to the trainer with a rope, then throw the tennis ball up and hit it with a racket.

Tip: avoid bouncing balls and don't hit yourself.