A article using yokomen shionage as a vehicle for understanding toppling.
The draw on ukes hand to topple them onto the toes for the omote version or rock themback on their heels for the ura version are both good example of the topple. Of course you can topple to heels or toes with either version but its not so clean and often becomes another technique.
Taking away all ok ukes power once the topple is setup allows you to pass beneath their blade (hand) and turn with out them having any weapons available.
Shionage is also a good exploration of moving the topple point around their base of support, it requires great sensativity, but then hey thats what the kata are for ...top develop skills and sensativity.