Why does the eagle kite have three lines?

Three lines are stable. The specific operation is as follows:

1. The first step is to pull out the hook on the reel, as shown in the figure below.

Step 2: Open the hook, as shown in the figure below.

3. Step 3: Hang the line hook on the strut, as shown in the figure below.

4. Step 4: Fasten the hook as shown in the figure below.

5. Finally, tie the kite string as shown in the picture below.