kosoto gari
In TCMA, it's called "踢(Ti) - forward kick". In Chinese striking art, it can be any kicks. In Chinese throwing art, it means that you use your
- instep to sweep behind your opponent's ankle, or
- inner foot edge to sweep/block your opponent's front lower leg.
Old Chinese saying said that if you can master "foot sweep", you should be able to deal with 80% of your opponent. It may be the most powerful throw in the throwing art. But since the timing and angle are so critical, it can be the most difficult one to develop.
There are over 30 different "foot sweep". It's one of the throws that can take care many different situations. You can almost write a book about just the "foot sweep".
Here is a simple no arm contact "foot sweep".
http://v.youku.com/v_show/id_XNDkyMTIzMDE2.html