Half Guard · Intermediate · Gi and no-gi

The underhook in half guard

From bottom half guard, the near-side underhook decides whether you come up beside the passer or are flattened under them, and it only counts from your side.

Position and problem

You are underneath in half guard with one of their legs trapped. The knee shield can hold the chest away, but it cannot by itself take you anywhere: sooner or later the distance closes or you decide to close it. At that moment one arm on each side is reaching for the same space, under the other person's armpit on the side of the trapped leg. If the top player wins it, they pair it with a crossface, your shoulders go flat, and every passing entry from half guard is open to them. If you win it, you can get your head and chest off the mat and come up beside them. When both players end up on their knees, hip to hip, with the bottom player's underhook against the top player's overhook, many gyms call the position the dogfight.

Objective

Win the underhook on the trapped-leg side, get onto your side and up to an elbow or a knee, and arrive beside the top player rather than underneath them.

Core concept

The underhook is a way of getting out from under the chest, not a grip to hang from. Its value is that it lets your shoulder come off the mat and your head travel to their ribs, which turns a pinned position into a side-by-side one where the person who is lower and further behind the other's hip tends to win. That is why an underhook taken from a flat back changes nothing: the arm is in the right place and the body it belongs to is still pinned, so the top player simply wraps it with an overhook, usually called a whizzer, and drives the shoulder back down. Sequence it the other way round. Get on your side, get the head low and close, and then the underhook is attached to a body that can move. The top player is not passive in any of this. The whizzer, the crossface and the front headlock family are all answers to the underhook, which is why the position is a fight rather than a technique.

Key mechanics

Be on your side before you swim the arm in. The shoulder on the underhook side has to be off the mat, or the underhook has no body behind it.
Reach deep: the hand goes to their far lat or around the waist, with your elbow high behind their armpit. A shallow underhook at the ribs is easy to whizzer and easy to pummel out.
Put your head low against their ribs or hip on the underhook side and keep it tight to them. A head that floats out in the open is available to the crossface and to the front headlock.
Keep hold of the trapped leg while you come up, and move your hook from a lockdown or a triangle to something you can base on. The legs stop them stepping away from the underhook; they also have to let you get to a knee.
Come up in stages: elbow, then hand, then knee. Each stage is a base you can stop on if the whizzer gets heavy, instead of one lunge that either works or collapses.
Once you are up, finish by getting behind their hip. Driving straight into them is a pushing contest with the person who has gravity; circling toward their back makes the whizzer the only thing holding them in front of you.
When the whizzer is too heavy to come up against, change the question. Dropping back under them, or freeing the arm and recovering the knee shield, keeps you in half guard with your shoulders still off the mat.

Common errors

Taking the underhook while flat on the back, so the arm is in place and the shoulders are still pinned under a crossface.
Holding a shallow underhook at the ribs, which the top player wraps with a whizzer and uses to drive the shoulder back to the mat.
Lifting the head up and away from the opponent while coming up, which puts the neck in the open for a front headlock.
Letting go of the trapped leg on the way up, so the top player backs out and the underhook is attached to nobody.
Pushing straight forward from the knees against the whizzer instead of circling behind the hip, and being driven back down by the heavier position.

Safety

Two exposures are specific to this position. The first is the neck of the person underhooking: a low head with an arm threaded under the opponent's armpit is the shape that arm-in strangles from the front headlock, the d'arce among them, are built around, and a hard crossface turns the head one way while the body is trying to come up the other. If an arm closes around your neck and your own underhooking arm together, deal with that before anything else, and tap to a neck that is being twisted rather than waiting to find out whether it is a strangle. The second is the shoulder of the same arm. A whizzer driven forward and down loads the underhooking shoulder from above with the elbow trapped high. When you are the one applying it, put weight on it steadily and never wrench it; when you are underneath it and the shoulder is being forced, pull the arm out and give up the underhook.

Training progression

Static: from bottom half guard on your side, partner holding still, swim the underhook in and place the head on the ribs. Check that the shoulder is off the mat before the arm moves.
Cooperative: partner gives the underhook and a light whizzer. Come up elbow, hand, knee, stopping at each stage for a breath.
Pummelling game: both players start flat-handed in half guard and fight only for the underhook on the trapped-leg side. Reset the moment either wins it cleanly.
Constrained sparring: bottom player starts with the underhook, top player may only use the whizzer and the crossface. Bottom player scores by getting behind the hip; top player scores by flattening both shoulders.
Positional sparring from the knees, underhook against whizzer, at full resistance in short rounds. Swap roles every round so both players learn what the other side feels like.
Live rounds from half guard, noting afterwards whether you lost the position at the underhook, at the head, or at the legs.