How to treat launching with pay-off level

1. First, according to the reflection method, observe the height difference between the upper and lower threads of the water level to see the launching height.

2. Secondly, observe the reflection of the upper and lower wires of the level, and keep your eyes at a certain distance from the reflection. Move your head to see the position of the horizontal upper and lower wires.

3. Finally, judge the launching height by lowering the steel wire.