The truth is...aside from all the silly things I've see..well..predominantly Korean instructors say that sequence is used for (one actually said it was used to block a sword....lol...let's just call him 'stumpy'), the technique is really a spring hip throw. The reason you kick is to pop the person's body up off the ground....and you aren't striking with the foot...you are laying your leg on the outside of theirs and the action of popping your leg straight is the driving force that makes the throw work. I'm not very good at the technique...but my sword master in Korea could literally may you plane out in the air just from popping his leg against yours. Then all he had to do was rotate with is hands and the next thing you were doing was trying to unplug your butthole from the wall where it shot across the room from your landing. LOL!

JH

This is the app I came up with : Your attacker comes in w/ a right lunge punch , at that time you would do a L. Kakie Uke ( hooking block ) , then come down w/ a R. downward elbow to the temple/corner of their eye , then you can either do the sidekick , or it can be a sweep instead .
Another app , that I was actually taught for this move , is if your opponent throws a R. Round kick at you , you deflect it , then side kick them back .
I personally like the Okinawan version of this move , grab their arm , and then either kick them in the arm pit w/ a toe kick , or break their leg w/ a kanstsu geri ( downward side kick ) .

David

This movement in Bassai is done slightly different in Shotokan. The movement starts from a left side forward knife-hand block (the previous move), and represents an opponent grasping your blocking (left) arm with his right (he is right side forward). You then execute a two-handed grasping block by reversing his grip on your left arm, and swinging your right arm in an exaggerated wide clockwise arc, from down low to as far over his head as your reach allows, while wrapping your right wrist over his trapped arm and pinning his grasping wrist to your forearm with your left hand. This forces him to bend the trapped wrist; then you pull both of your arms straight downward and inward, thereby performing a wrist lock on his trapped right arm. The wrist lock will immobilize him, forcing him to bend both his forward elbow and his forward knee. Please note that this technique is accompanied by an overshift to your left of the contracted front stance. Then immediatley pull both your arms (and subsequently his trapped arm) to your abdomen, rotate slightly and execute a low-level side thrust stamping kick to his forward knee.

I know this is a rather convoluted description of what has proven to be a very effective technique, but words can only do so much. This technique does have its limitations though, especially if the opponent is much taller than you are, as it will be difficult to get the wrist lock on him if he is not forced to bend his wrist during the movement. In that case, I would just shoot him instead.

Kyoshi