Approaching a 12" ledge, aggressive riding position, picking up speed. Note body position relative to vertical line through crank.

Rider rises up tall, shifts body back. The rider has moved back in relation to the crank line -- the center of gravity is between crank and rear wheel.The body is now fully back as the rider pulls up firmly on the handlebars. Front wheel in the air. Rider still pedaling. White lines show butt high off seat, eye to stem distance shortened.

Front wheel touches down, and rider is moving forward. Still pedaling. Rider pushes higher while rear wheel still on ground. Note seat to butt clearance.Rider moves further forward, pushing handlebars down. Eye to stem distance widening. Rider's center of gravity at highest point now.Rider's weight moves still further forward onto handlebars, body begins to angle downward. Rear wheel weightless; rebound may make it leave ground.

Body continues forward and down. The rider's downward motion acts as a lever to "fly" the rear wheel up. The seat is rising up under the rider.Rear wheel hitting the edge. The rider's downward motion is complete. Seat under rider, but still no weight on it. Note tire shows no "bulge" on sharp edge.Attack complete. Rider moves back to original riding position, body comes back up. Still pedaling.
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The key to the rollover is to keep all weight off the handlebars, the tension off the front brake, and the body upright relative to gravity while the bike does the rotating. Once you've recovered your balance, reapply the brakes.Keep your body upright and weight centered directly over the crank, and let the front of the bike fall away from you as it drops over the edge.
Just before the drop, let off BOTH brakes. Balance your weight on your feet. As the front wheel approaches the edge of the drop, compress the bike down through the pedals. As the bike's front end rebounds, pull up very slightly on the handlebars.Compress to unload both wheels simultaneously, lift handlebars slightly, legs near-straight, body over crank, arms controling "pitch" of bike.
If it's a major drop, straighten your legs, getting ready to absorb the hit at the bottom. Don't lock the legs straight -- keep the knees slightly bent. As the bike drops, control your attitude (tilt of the bike relative to the tilt of the slope) by pulling up or pushing down on the handlebars.Rear wheel should touch down first. Both feet absorb equally, hands control "pitch" of bike in the air, then angle of body during impact. Notice front and rear shocks equally compressed, front and rear tires equally "squished."
The bike should continue straight on its forward path (or even tilt upward a bit) until the rear wheel leaves the edge. The slower you're going, the more pronounced the weight transfer and handlebar support needs to be. The faster you're going, the easier it is.When done right, the bike should contact the ground level, or with a bit of rear tire first. Body leaning back slightly, butt a bit behind the seat. Arms pull upward to support the front of the bike as it leaves the edge.
Center of gravity is straight over the crank, feet level, arms relaxed so they can control the "pitch" of the bike. Wheels are lining up for landing -- the bike will rotate a bit so the rear tire hits before the front tire.