The plastic cable guides on the ends of a window regulator mechanism. I was sick of buying a replacement about once a year so I thought I would try to make my own. I believe the part can be mirrored to fit at either end. The pegs and the holes were tight, so you may want to tinker with the design to alter the fit. I printed in abs at 30% infill and 4 walls, it seemed very stiff and has held up so far.
The author marked this model as their own original creation.