Try to put your legs at the right height, windows, walls, etc. Generally speaking, it is recommended that people over the age of 16 adopt the static pressure method: keep one leg pressed for 30 seconds, and then change the other leg, and press each leg for about 5 times.
Then you need to fully stretch the ligaments of your body. After all, the split action needs the cooperation of all ligaments, and the static pressure method is also used. Leg press's principle is: acid adds pain. Otherwise, it will hurt the ligament!
Then gradually try the vertical fork, the front legs are fixed, and the rear legs are gradually moved back. Pay attention to non-slip!
Forks need enough willpower. You need to find a little friend to press it for you. A fork can help you open your crotch. Whether it's beautiful dance or cool leg technique of martial arts, you need to open your crotch. If you practice at a certain time, you will succeed. Don't give up practicing after success. You should persevere and challenge the opening of ligaments with greater difficulty, not limited to 180 degrees. It's a good idea to pad it with something like this in the picture!