BORETS
In this guide
A duck-under uses an opening under the opponent’s arm to reach an angle behind them. It works best when the setup, level change and footwork happen together. Simply bending your head under a tight arm leaves you stuck. Learn the entry first, then practise establishing control behind the opponent before adding a takedown or BJJ follow-up.
Read the opening rather than diving at it
Hand fighting can create an opening when the opponent reaches, raises an elbow or changes pressure through a tie. The opening may be brief, so your stance needs to let you move without first reorganising your feet. Watch the arm and the opponent’s body together; a raised elbow is not useful if the hips are already too far away.
For early practice, ask a partner to provide the same controlled reach or tie each time. Learn what the available space feels like before the partner varies it. If you have to force your head through a closed gap, reset the setup rather than treating resistance as a challenge to push harder.
Coordinate arm control, level change and the step
Use the arm control taught for your variation to guide the opening, lower your level and step toward the available angle. These are connected actions. Trying to lift the arm first and walk through later gives the opponent time to recover position.
Guide rather than jerk the shoulder. The partner should understand where you are moving and remain able to respond. Different ties lead to different footwork, so practise one coherent version before combining details from several demonstrations. A few controlled repetitions on each side reveal whether the sequence is balanced.
Keep the head and hips moving together
Lower through the legs instead of collapsing forward at the waist. Keep the neck comfortable and the head moving with the trunk. Looking violently upward while ducking, or forcing the crown into a partner, does not create a better route through the opening.
Bring your hips and feet around the angle rather than leaving them behind while the head reaches through. If the opponent can turn and face you before your feet recover, examine the distance and the size of the step. The aim is a balanced angle, not the lowest possible head position.
Secure the position before choosing a finish
In early drills, stop after reaching a balanced position behind the partner and establishing the agreed control. That makes it easier to see whether the entry actually worked. A loose chase around the back is different from control that survives the opponent turning or moving away.
A mat return is a separate skill requiring suitable space, a partner who knows how to receive it and coached practice. Do not add an uncontrolled lift or backward arch because you reached the rear body lock. In BJJ, protect against the opponent turning and build an appropriate back-control transition; jumping onto a standing partner is not a default beginner finish.
When the opponent turns in
If the partner faces you before you secure control, recover a useful stance and inside position. A coach may connect this reaction to another entry, but a beginner can first learn to exit cleanly and restart. Continuing to twist under a closed arm often makes the position worse.
Use a drill with two possible outcomes: the opening stays available, or the partner turns to close it. Your task is to recognise which occurred. Score the practice by making the right decision, including a reset, instead of insisting that every attempt end in a takedown.
Adapt grips for gi and no-gi
No-gi practice commonly uses contact with the arm and upper body. Gi grips can change how you create and maintain the opening, but they can also restrict your own movement if you keep a grip too long. Ask which connection should remain and which should release as you pass the arm.
Use legal grips for the event: IBJJF rules prohibit placing fingers inside sleeve or trouser openings and restrict clothing grips in no-gi. The existence of a sleeve handle does not justify pulling sharply against a fixed shoulder. Maintain the same controlled progression when adding fabric grips.
Build from a known response to a short live task
Start with several cooperative entries, pausing at the finishing angle. Next, let the partner vary the timing of the reach. Then add the option to turn in and practise recognising a closed opening. Finish with short, controlled rounds whose only goal is reaching the angle; add takedown finishes separately when both partners are ready.
Progress according to control rather than a fixed number of weeks. A stable video can help a coach see the entry and footwork, with everyone’s permission. BORETS LAB is preparing its online school; register to follow the launch, check membership availability and use the public guides and YouTube channel for focused study between classes.