Recently these very good videos of RH Gutierrez M.D. discussing the Okinawan toe kick of Aragaki, presented this material in a very clear manner.
Now the toe kick is used by various Okinawan systems, but there are various ways to approach it.
A series of great articles at FightingArts.com by Christopher Caille does a very good job discussing this, and is worth your time reading this.
This is something I have discussed before:
As time moves on I am sure there will be more on this topic discussed.