Another Columns variation. In the Rainbow Cross the balls were thrown to the other side of the pattern, in this trick the hands carry the balls across.
Hold two balls, one in each hand.
Stand with your elbows sticking out from your body & your hands pointing inwards towards each other. Without throwing the balls, scoop both hands inwards so that one crosses underneath the other, your forearms should meet & just touch at halfway between the hand & the elbow (your arms don't have to touch each other, the touching just acts as a guideline). Your elbows should move inwards too & end up just above & level with your hips. Finish with both hands pointing away from you & out to the opposite sides.
With your arms crossed move both arms as one, don't bend your elbows but use your shoulders to move your hands so that they rise straight up, when doing the actual throw it feels as if you are 'lifting' the balls into the air. Bend your wrists back a little to keep the backs of your hands level with the ground.
Practise putting the two parts together into one smooth movement. Then do the move & throw the balls so that they rise in two columns, peak at the same height & remain an equal distance apart all the time that they are in the air. Uncross your arms & catch both balls.
Your biggest problem will be the balls flying apart or together, turn your wrist inwards as you release a ball to correct an outward throw, flick your fingers open as you release to correct an inward throw. If you are throwing one ball forwards, flick harder with your index finger as you release the ball, or with your little & ring fingers if you are throwing backwards. If one ball doesn't peak as high as the other try swinging & touching your arms together at a lower point to allow you to make a longer 'lift'. If you move your arms together as a single unit the balls will also rise together.
Practise the move with your arms crossed both ways, right over left & left over right.
Juggle columns, as you throw the centre ball catch the two outside balls, swing & cross them underneath the middle ball & toss them together as it peaks. Uncross your arms & resume the columns pattern.
The crossunder is also used in Mills Simultaneous 1 & Mills Simultaneous 2.