What is the Duck Under?
A duck under changes levels, pops under their elbow or collar-tie arm, and circles behind to a rear body lock or mat return. In BJJ it pairs with arm drags, snap-downs, and collar-sleeve fights when opponents overextend upper-body ties.
Create the Opening
You need an elbow or tie to slip under.
- Engage collar tie, wrist control, or arm drag
- Force their elbow up or their posture overextended
- Change levels under the arm line
- Keep your head safe from front headlock traps
Circle Behind
- Pop the head and shoulder under the armpit
- Step around their hip corner
- Lock a rear body lock
- Prevent them from re-squaring
Mat Return / Back
Finish position matters more than the duck itself.
- Mat-return or sit them to the mat
- Establish seatbelt control
- Insert hooks for back control
- Only then hunt the rear-naked choke
Key Grips & Control Points
- Control of the wrist, elbow, or collar tie you will slip under
- Head and shoulder path that clears the armpit line
- Hands locking a rear body lock as you circle behind
- Hip connection that stops them from turning back into you
Timing & Movement Cues
- Duck when their elbow rises or the collar tie posts high
- Enter as they reach for your head or overcommit a snap
- Circle behind before they can re-square their hips
Pressure & Weight Distribution
- Level change first; do not bend at the waist into their chest
- Keep moving around the corner — a stalled duck becomes a front headlock fight
- Lock hands behind them and mat-return or sit to back control
Typical Counters to Expect
Follow-Up Options
- Rear body lock mat return to back control
- Seatbelt and hooks when they hit the mat
- Single-leg or high crotch if they block the circle early
Setups & Entries
- Arm-drag entries that expose the near elbow
- Collar-tie pummel that lifts their elbow
- Snap-down threats that make them overpost the head
Training Drills
- Level-change duck-under circles to rear body lock
- Arm-drag to duck-under chains
- Mat-return and hook-set from rear body lock
Coaching Notes
- Clear the armpit, then circle — do not stay in front
- Hands lock behind before you celebrate the angle
- If the duck stalls, abandon into a cleaner shot or snap-down
Related Study
Connect this movement with complementary positions and attacks.
Summary
Duck under slips under a high elbow or collar tie, circles to a rear body lock, and finishes with a mat return to the back. Level change cleanly, lock hands behind, and abandon early if they drop the elbow and trap your head.