2 Blockers start on pos. 2 and 4.
1 Blockers starts on pos. 3

The Blocker on Pos. 3 blocks by himself, and immediately afterwards goes with a 3-Step to Blocker on Pos. 2, they make immediately a double block.
After this block the Blocker on Pos. 2 goes out and runs to the back of the court (waiting line). The blocker who came from Pos. 3 stays as new blocker on Pos. 2.

Right after the Blocker on Pos. 3 has left the middle another blocker from the waiting line steps in, makes a block in the middle and goes then for a double block to pos. 4.