1. Circle walking - force your opponent to move with you so you can take advantage on his weight shifting. Soon or later you will find the correct angle to sweep your opponent's leading leg when he puts weight on it.
2. Single palm change - You use leading arm to attack, your opponent blocks it, you use back arm to block his block, free your leading arm, you then continue to attack with your leading arm.
3. Use in sparring - When your back foot, your opponent's leading foot, and his back foot are all in one straight line, if you shoot at his leading leg from this angle, it will be harder for him to pull his leading leg back. Even if he may try to do so, his leading leg will always be in your attacking range. Also from this angle, his back hand will be difficult to reach you. You only have to deal with one of his arms instead of both of his arms.