A simple square trim piece to clean up a square hole. A little super glue on the underside of the upper lip has worked perfectly to hold mine in place. 

I made this to run cords out the bottom of my DIY printer enclosure. If you need to raise your enclosure a little off the ground for the cords to run, you can find the feet I made here. 

The outer diameter of the lower section is 1.5"x1.5", so it should fit a square hole cut slightly bigger than that. 

Find the model on OnShape here.