If you want to start a heated debate among Rappel Rack aficionados just ask the group what style is best, J-Racks or U-Racks? Both share benefits such as providing the largest range of friction control with a variety of ropes, being great as either a lowering device or on rappel, not twisting ropes and so on. The benefit that people most often attribute to the U-Rack over the J-Rack is greater strength. This is a fallacy, despite being the common understanding, as the system fails when the rope brakes rather than the device breaking. As a result, both types of racks achieve similar ratings.
U-Racks are used in the opposite orientation as J-Racks in that the rack is clipped to the harness or anchor at the bend area of the frame with the “legs” always pointing away from the user. The U-Rack does not facilitate friction variation by dropping or adding bars as the J-Rack does and the U-Rack should never be used with less than 4 bars. The benefit of the SMC designed 4 bar U-Rack is having the two opposed tied-off bars. This provides the opportunity for quicker tie-off methods (user can braid the rope between the 2 pins much like a boat cleat is used) and the user can have more “fine tuned” friction possibilities on a shorter and lighter system. The 6 Bar version utilizes a single Tie-Off Bar and 5 Brake Bars.