This is the last significant rapid of the run. You have door 1, door 2, and door 3.... Well really you can run combinations of each line. The rapid consits of a upper part which has three lines and a lower part which has three lines. Mix and match all you want for the same price. The right line is more creeky and channalized and the left line is a little more beefy. At flows over 2.2 its hard to distinguish any lines.