World 1 - Level 6
Boulder Blockade

To free Stinky, roll two boulders along the yellow path, then the third boulder along the red path.

Next, move all three boulders from left to right (but do not step on the conveyor belt yet!). This will clear a path for Loof along the purple arrow. Move Loof into this path and push one (and only one!) boulder pack toward the left. Immediately move one step up (not down!) as the boulder will bounce off the conveyor belt and roll back. Now push the boulder into the water below. Repeat with one more boulder, this clears both the path for Stinky, as well as a path to the Bonus Coins below.