You can hold the threaded sleeve with your right hand. If the helix angle of the thread faces the thumb, it is a positive thread; If it's the opposite, it's anti-silk.

The positive wire must be connected by rotating the steel bar, but it is not convenient to rotate the steel bar in some parts (such as the long bend at the end of the roof beam). ), so you need positive and negative lines to complete at this time. The so-called reverse thread is not that all threads are reversed, but a positive thread and a negative thread. Know the direction clearly when connecting.