The Knee Slice with Underhook represents one of the most fundamental and high-percentage methods of passing half guard in modern Brazilian Jiu-Jitsu. This technique combines two powerful control mechanisms: the cutting action of the knee slice and the dominant positioning provided by the underhook. The underhook prevents the bottom player from recovering guard while the slicing motion of the knee creates separation from the remaining half guard hook, allowing the passer to achieve side control.
What makes this pass particularly effective is its ability to neutralize the bottom player’s primary defensive tools. The underhook eliminates their ability to come up on their side or recover full guard, while the knee slice prevents them from retaining the half guard hook or transitioning to other guard variations. This dual-layered control creates a passing sequence that works across all skill levels, from fundamentals classes to world championship matches.
The technique exemplifies core guard passing principles: control before movement, systematic progression through stages, and maintaining constant forward pressure. Unlike explosive or athletic passes, the knee slice with underhook relies on positional dominance and technical precision, making it accessible to practitioners of all body types and athletic abilities while remaining devastatingly effective at the highest levels of competition.
Starting Position: Half Guard Ending Position: Side Control Success Rates: Beginner 45%, Intermediate 60%, Advanced 75%
Key Principles
- Secure underhook control before initiating the slice to prevent defensive recovery
- Maintain constant forward pressure throughout the pass to flatten opponent
- Use the knee as a wedge to separate and clear the half guard hook
- Keep chest pressure tight to opponent’s upper body to prevent space creation
- Drive the slicing knee across opponent’s thigh line, not straight down
- Consolidate side control immediately upon clearing the legs
- Maintain head position on the underhook side to prevent opponent’s turn
Prerequisites
- Top position in opponent’s half guard with at least one leg trapped
- Established underhook on the near side with deep penetration
- Free leg positioned to begin knee slice motion across opponent’s thigh
- Upper body pressure preventing opponent from coming to their side
- Crossface or head control on far side to limit opponent’s mobility
- Hip positioning close to opponent’s body to minimize space
Execution Steps
- Establish underhook control: From top half guard, drive your near-side arm deep under opponent’s armpit, achieving an underhook. Your hand should reach toward their far shoulder, creating maximum depth. Simultaneously use your opposite hand to establish a crossface or control their far-side arm, preventing them from framing. (Timing: Before any passing motion begins)
- Position the slicing knee: Place the knee of your free leg on the mat at a 45-degree angle, positioned near opponent’s trapped knee. Your shin should be angled to cut across their thigh line. Keep your toes flexed and base positioned for drive-forward power. Your trapped leg should be working to extract from the half guard hook. (Timing: As you secure underhook depth)
- Drive forward and flatten: Using the underhook, drive your chest forward and down onto opponent’s upper body, flattening them to the mat. Your weight should be distributed through your chest and the underhook-side shoulder. This forward pressure is critical - it prevents them from coming to their side or creating defensive frames. Keep your hips close to theirs. (Timing: Before beginning the slice motion)
- Begin the knee slice: Drive your slicing knee across opponent’s thigh in a diagonal cutting motion, moving from their hip toward the mat on the far side. The motion is similar to closing a scissor blade. Your knee should maintain contact with their thigh throughout, acting as a wedge to separate their legs. Simultaneously, extract your trapped leg by pulling it back and up. (Timing: Once opponent is flattened)
- Clear the hook and transition: As your knee completes the slicing motion, your trapped leg should pop free from their half guard hook. Immediately bring this leg over their bottom leg, positioning it on the far side of their body. Your slicing leg extends and steps over, establishing a wide base. Maintain underhook control and chest pressure throughout this transition. (Timing: At completion of the slice)
- Consolidate side control: Land in solid side control position with your chest across opponent’s torso, underhook still secured, and crossface established. Your hips should be low and heavy on their near hip. Adjust your base with legs spread wide for stability. From here, transition to standard side control grips and begin advancing to more dominant positions. (Timing: Immediately after clearing legs)
Opponent Counters
- Opponent obtains underhook on same side, creating a battle for underhook control (Effectiveness: High) - Your Response: If you lose the underhook battle, immediately switch to a different passing strategy like the long step pass or knee cut. Alternatively, establish a whizzer over their underhook and transition to a different angle of attack. Never fight a losing underhook battle - adapt and change angles.
- Bottom player turns to their knees and comes up on the underhook, recovering to dogfight or attempting a sweep (Effectiveness: High) - Your Response: Prevent this by maintaining strong forward chest pressure before beginning the slice. If they start coming up, abandon the slice temporarily, drive them back down with shoulder pressure, then re-initiate. You can also transition to front headlock control if they fully commit to coming up.
- Opponent inserts their far-side knee shield or frames with their bottom leg to prevent the slice from completing (Effectiveness: Medium) - Your Response: Address the knee shield by using your crossface hand to push their knee down and away, or transition to a knee cut angle instead. If the frame is strong, lift your slicing knee slightly to step over their defensive leg rather than fighting through it directly.
- Bottom player grabs your slicing leg or ankle, preventing forward motion (Effectiveness: Medium) - Your Response: If they secure a grip on your leg, temporarily base out wider with that leg and use increased chest pressure to flatten them. Break their grip by circling your leg or using your free hand. Once the grip is broken, immediately resume the pass before they can re-establish defensive controls.
- Opponent attempts to roll through or invert to recover guard (Effectiveness: Low) - Your Response: This desperation counter rarely works against proper underhook control. Maintain your underhook depth and chest pressure, follow their motion slightly, and the roll will fail. Their own momentum often helps complete your pass. In rare cases where they commit fully, you may take their back.
Test Your Knowledge
Q1: Why is establishing the underhook considered more important than beginning the slicing motion immediately? A: The underhook provides the positional control that prevents the bottom player from coming to their side, recovering guard, or creating defensive frames. Without a deep underhook, the opponent can easily turn into you, establish their own underhook, or use the space to recover. The underhook is the foundation that makes the slice mechanically effective - it pins their upper body while you work to clear their legs. Attempting to slice without securing the underhook first results in a battle rather than a systematic pass.
Q2: What is the correct angle for the knee slice motion, and why does this angle matter? A: The knee should slice at approximately a 45-degree diagonal angle across the opponent’s thigh, moving from their hip area toward the mat on the far side. This angle matters because it creates a wedge effect that separates their legs rather than simply applying downward pressure. A straight-down motion gets stuck in their half guard hook and fails to create the lateral separation needed. The diagonal cutting motion mimics a scissor blade closing, progressively opening their legs while maintaining forward progress toward the pass completion.
Q3: How should you respond if the opponent obtains an underhook on the same side during your passing attempt? A: If you lose the underhook battle, you should immediately abandon the knee slice with underhook technique and transition to an alternative passing strategy rather than fighting a losing underhook battle. Options include switching to a long step pass to the opposite side, establishing a whizzer over their underhook and working a different angle, or resetting to a neutral passing position. Fighting for an underhook you’ve already lost wastes energy and gives the opponent time to mount offensive attacks. Adaptability is more important than stubbornness in guard passing.
Q4: What are the two primary control points that must be maintained throughout the entire knee slice with underhook sequence? A: The two primary control points are the underhook on the near side and either a crossface or far-side shoulder control on the opposite side. These two points of control, working in conjunction, pin the opponent’s upper body and prevent them from creating the frames or turns necessary to defend. The underhook prevents them from coming to their side, while the crossface/far control prevents them from turning away or establishing distance. If either control point is lost, the pass becomes significantly less effective and the opponent gains defensive opportunities.
Q5: Explain the relationship between hip position and passing success in the knee slice with underhook? A: Hip positioning is critical because distance equals defensive opportunity for the bottom player. Your hips must remain close to the opponent’s body throughout the entire passing sequence - maintaining hip-to-hip contact eliminates the space necessary for them to insert frames, turn, or recover guard. When passers keep their hips too far away, they create a gap that allows the opponent to insert their knee shield, establish frames with their legs, or turn into the passer. The principle of ‘chest to chest, hip to hip’ ensures that you’re controlling through connection rather than attempting to control across distance, which is mechanically inefficient and easily countered.
Q6: Why is forward chest pressure considered equally important to the slicing motion itself? A: Forward chest pressure serves as the mechanism that prevents the opponent from achieving the vertical space necessary for effective defense. When the bottom player is flattened by constant forward pressure, they cannot come to their side, cannot create frames effectively, and cannot generate the leverage needed for sweeps or guard retention. The slicing motion clears the legs, but without chest pressure, the opponent maintains the mobility to continuously replace their guard or create scrambles. The pressure must be maintained throughout the entire technique - any momentary decrease allows the opponent to create defensive space.
Safety Considerations
The knee slice with underhook is a relatively safe technique compared to submissions or more explosive passes, but practitioners should be mindful of several safety considerations. When executing the slice, avoid driving your knee aggressively into opponent’s thigh in a way that could cause bruising or impact injury - maintain constant contact but don’t spike the knee downward with force. The crossface should be applied with the blade of your forearm across their jaw/neck area, never with sharp elbow or forearm bone pressure that could cause neck injury. When drilling with newer partners, use controlled pressure rather than maximum force, as heavy chest pressure can be uncomfortable and potentially restrict breathing if applied incorrectly. Partners on bottom should tap if they feel unsafe or unable to breathe, and top players must respond immediately to any tap. Avoid cranking the underhook upward in a way that hyperextends the shoulder - the underhook is for positional control, not a submission. When training with significant size or strength disparities, the larger/stronger player should modify their pressure to allow the technique to work based on position rather than pure force, which develops better technical proficiency and keeps training partners safe.
Position Integration
The knee slice with underhook is a cornerstone technique in modern guard passing systems and serves as a primary method of advancing from half guard to dominant top positions. Within the context of a complete passing game, it functions as one of several interconnected options when facing half guard, creating pressure-passing sequences when combined with techniques like the long step pass, crossface pass, and smash pass. The underhook control established in this technique can also transition to alternative positions - if the pass is defended, the underhook provides the foundation for taking the back, establishing a dogfight position, or transitioning to other guard passing angles. The technique integrates seamlessly into both gi and no-gi grappling, though grip configurations differ slightly. From a conceptual standpoint, this pass teaches fundamental principles that apply throughout BJJ: establishing dominant controls before advancing position, maintaining constant forward pressure, and systematically removing opponent’s defensive tools. Many high-level competitors build entire passing systems around variations of the knee slice with underhook, using it as the technical foundation that other passes branch from. Understanding this technique deeply improves overall passing ability because it teaches the relationship between upper body control and lower body clearing - a principle that applies to virtually all guard passes.
Expert Insights
- Danaher System: The knee slice with underhook represents one of the most mechanically sound approaches to passing half guard because it systematically removes the opponent’s defensive hierarchy. In any guard passing situation, your primary concern should be establishing dominant grips and positions before attempting to advance - this technique exemplifies that principle perfectly. The underhook eliminates approximately seventy percent of the bottom player’s effective defensive options by preventing them from coming to their side and establishing their own underhook or frames. Once this control is secured, the slicing motion of the knee acts as a mechanical wedge that progressively separates their legs while your chest pressure prevents vertical escape. The beauty of this technique lies in its scalability - the same mechanical principles work at beginner level and world championship level, though the details and pressure become more refined with experience. When teaching this pass, I emphasize that the underhook is not simply a grip but a positional checkpoint that must be achieved before any passing motion begins. Students who rush past this checkpoint invariably struggle with the technique, while those who prioritize the underhook find the pass becomes almost effortless once proper positioning is achieved.
- Gordon Ryan: The knee slice with underhook is one of my highest-percentage passes in both gi and no-gi competition because it’s incredibly difficult to defend when executed with proper pressure and timing. What makes this technique so effective at the elite level is that it puts the opponent in a constant state of defensive crisis - they’re simultaneously dealing with upper body control from the underhook and crossface while their legs are being systematically cleared. I’ve finished matches at ADCC and other major competitions using variations of this pass because it works against the best guard players in the world when you commit fully to the pressure. The key detail that separates beginner and advanced execution is the chest pressure component - you need to make the opponent feel like they’re being crushed, not just passed. If they can breathe comfortably and move freely, you’re not applying enough forward pressure. I also like to chain this with the long step pass, so if they manage to defend the slice by turning into me, I’m already positioned to attack the other side. The underhook-to-pass connection is fundamental to modern guard passing at the highest level, and this technique is the clearest expression of that principle. When drilling, focus on making the position feel hopeless for your partner - that’s the level of control you need in competition.
- Eddie Bravo: While the knee slice with underhook is definitely more of a traditional pressure passing technique than what we typically emphasize in 10th Planet, I respect its effectiveness and teach variations of it to my students, especially for no-gi competition. What I find interesting about this pass is how it creates opportunities for submission chains if the opponent defends in certain ways - if they try to come up on the underhook, you’re in perfect position for a guillotine or darce choke. If they turn away, you can sometimes catch them with an arm triangle or take their back. So while the pass itself is straightforward, the strategic implications are deeper than they appear. One modification I like is to combine the knee slice mechanics with more dynamic movement - instead of purely pressure-based execution, sometimes exploding through the slice creates a different timing that catches guard players off-guard, especially those used to defending slow, methodical pressure passing. The underhook control is universally valuable regardless of your stylistic preferences. In our system, we might flow between rubber guard attacks, lockdown, and other half guard variations, but understanding how to pass half guard with an underhook makes you a more complete grappler. It’s one of those techniques that every serious competitor should have in their arsenal, even if it’s not their primary strategy.