Folders is the 7th stage of Beginner Extra in Super Monkey Ball 2 (17th in Super Monkey Ball Deluxe), the 10th stage of Boiling Pot in Story Mode (17th in Super Monkey Ball Deluxe), and the 57th stage of Ultimate without continues.
This stage is made up of fifteen rectangular platforms with railings on the sides. The platforms are next to one another and are either flat or collapsed down at a 90 degree angle, changing every couple of seconds. The railings doesn't collapse.
To get the Blue Goal, head onto the right-side or left-side railing. Continue to the end without touching the rest of the floor at all. Wait for the last platform to collapse and head back up. Then, dash through the goal.
Roll up on the right side of the stage, then the left, and then the right again, and hit the first folder on the right edge as it is coming up. Then, hit the left edge of the folder on which you bounce. Then, if you have done it right, you will go straight in the goal while getting a few bananas. Moreover, an easier way to do this is to bounce on a railing instead of the folder after you have been hit by the first one.