This is a clip to attach the johnniewhiskey cable chain (https://www.thingiverse.com/thing:2920060) to the X gantry. Many other brackets are available for this purpose, but mine is different. It is very easy to fit - you just clip it around the extruder stepper, attach the cable chain, and zip tie the X cable where it exits the channel. No need to disassemble the extruder or the Z rod. This also has the benefit of leaving the other commonly used attachment methods free for filament guides etc. It also doesn't need any supports to print.
Update: I have added a tweaked version as the original bent out of shape after a while. It is stronger but you have to remove the stepper to fit it. You might also need to clip a bit off the last chain link to make it fit.