Practice with caution to avoid injury
With your guard up, raise one knee across the body to make contact with the opposing inner forearm. The swing the knee across to contact the other inner forearm before dropping the leg back to a standing position.
The basic blocking system is used to teach the beginner how to defend against various attacks. The blocking system is also used to develop the student's strength and functionality. Once the core understanding of the technique is achieved, it evolves with the practitioner's understanding, later encompassing striking, joint-locks, etc..