Here, juggler B (we can see his hand on the right), is in front of juggler A (we cannot see him on the left) and is taking with his left hand (in pink) a club thrown from A's right to their left hand. In the meantime, B replaces the club they just took with another one (purple) with their left hand and puts it in the left hand of A. Their right arm then goes above the left arm.
For A, nothing has changed, apart from an exchange of clubs. The movement can be done with every club that arrives to the left hand of A; B making a quick handacross from one hand to another between each takeout (the club taken with the left hand will be given back to A with the right hand the next time). B has then to continue quite quickly, A has to try to slow the pattern and overall keep throwing their clubs at the same height.
If this is successful, B can attempt the handacrosses behind the back. A third juggler can also be added, doing the same as B but on the right hand of A.