A Gake is a blocking hook that Uke is generally pushed over, and generally involves the entire leg.
A Gari is a reap that pulls the attacked leg out from under Uke, generally just with the foot or lower leg.
Tori's leg hits Uke's leg and stops - Gake
Tori's leg hits Uke's leg and follows through - Gari
It may sound picky but they really do describe very different attacks, at least as different to us as a Baseball choke and an X-choke.