This is a combat concept.
(Skillfully avoiding the obvious jokes) nobody has 3 legs like a stool or a tripod.
If you wobble a tripod it's balance will redistribute to the 3rd leg.
Wobble a person and they have to either step to where the third leg isn't or they fall over.
This is Third Point theory - the place where there is no leg.
Throw your opponent to the third point without allowing him to step to regain his balance and he will fall that way.
This applies to throws and well as projections
think about o soto gari, outer reap - we use tsurikomi, push-pull, to off balance him and take him back to third point
kote gaeshi wristlock projection - where you point the palm is here he will fall
a sweep inside a karate ABC or kempo set - he falls to the third point
a silat sweep inside or outside a trap
