Ko-soto-gake (minor outer hook) is a foot technique from the third group of the gokyo. Tori hooks uke's heel from the outside with the foot and drives uke backward by moving the whole body forward. Where ko-soto-gari reaps, ko-soto-gake blocks and pushes. It has a heavyweight feel to it, though lighter players use it very well too.
Gari or gake: the word changes the technique
Both throws attack the same leg from the same side. The difference is in the verb. Gari means reap. Tori's foot sweeps uke's heel toward the toes, uke loses the support and falls. Gake means hook. Tori's foot sets behind the heel (or the bottom of the calf) and stays there, while tori's body does the work by moving forward.
In practice, you pick ko-soto-gake when uke's weight is planted on the rear leg, too heavy to reap. If you are not yet comfortable with ko-soto-gari, start there. Both sit among the ashi-waza in the nage-waza, and the gokyo puts them one group apart.
Backward kuzushi comes first
For a right-hander hooking uke's right leg with the left leg, the kuzushi goes to uke's rear right corner. Uke's shoulders go back and the weight sinks onto the right heel.
The hands work together. The tsurite (right hand on the lapel) pushes back and down, forearm against uke's chest. The hikite (left hand on the sleeve) does not pull toward you. It follows down to close off uke's right side. Without that sleeve control, uke steps sideways and the throw disappears. The general principle is covered in kuzushi, tsukuri and kake.
How to do ko-soto-gake
The movement has three beats.
Close the distance. Tori steps the right foot in close to uke to bring the hips together. Short distance, stomachs almost touching.
Hook. The left leg goes behind uke's right leg. The sole or instep sets behind the heel, tori's knee slightly bent. The foot stays still.
Drive. Tori moves all the body weight toward uke's back, in the direction of the trapped heel. The hands push the same way. Uke falls on the back, and tori stays standing or follows uke down to keep working.
What goes wrong most often
Hooking too high, at the knee, turns it into a weak o-soto-gari with no reap. Hooking too early, before the weight is on the heel, gets you nothing. So does staying at a distance and pushing with the arms alone: uke steps back and the throw is gone.
The most common fault in lower grades is where tori looks. Tori watches the foot. The chest leans forward, the push becomes vertical, and uke only needs to lean in to flatten tori on the mat.
Combinations and counters
Ko-soto-gake often works as the second beat. After a forward attack (uchi-mata or harai-goshi) that uke blocks by pulling the hips back and arching, uke's weight is already on the heels. All that is left is the hook. The o-uchi-gari into ko-soto-gake combination also flows naturally. Uke pulls back the attacked left leg and shifts weight onto the right, which you then block.
As for counters, an uke who feels the hook early can lift the leg, leave tori's foot in empty space and go into a hip technique. Tori is then on one leg and leaning back. So never stay hooked without driving.
Where to use it depending on your grip
In same-side stance (right-hander against right-hander), ko-soto-gake goes on uke's lead leg as the foot lands after a step. In opposite stance, uke's right leg is further away. You need a deeper entry, and it suits judoka who are already comfortable at short range.
Three drills to feel the hook
Face to face with a static uke, tori practices the hook alone and looks for the feeling of a trapped heel, with no push. Next, uke walks backward and tori hooks as the foot lands. Finish with a combination drill: tori attacks forward, uke resists by stepping back, tori hooks.
A practical tip: film yourself once from the side. If your hip is behind your supporting foot when you push, the throw will not hold up in randori. Bring the hip forward first, then drive.