The CrazyFly Depower Line is the line that you use to trim the power of your kite on the Crazyfly Sick Bar. These lines wear down over time with use, and it's a cheap and easy part to replace to ensure your bar is top notch condition.
For 2011-2014 Sick Bars, the depower line is a double-duty line for both the kite trim and bar sheeting. It starts at the back of the trim cleat, runs down through the bar, through the top of the chicken loop, then goes back up through the bar up to the bracket where the front lines connect, and finally down through the front "teeth" side of the cleat where the grab handle hangs.
For 2015 and newer Sick bars, the depower line starts above the PU-coated bar sheeting line inside the cleat, then goes up to the bracket where the front lines connect, and finally down through the front "teeth" side of the cleat where the grab handle hangs.