About this 3D model
This is my take on Chipguy's T-post insulator https://www.thingiverse.com/thing:1440228. I was afraid that the insulator would arc when wet so I decided to run the wire through a high voltage tubing such as the tubing available from Tractor Supply or other suppliers of electric fencing materials. Tractor Supply's tubing measures 8 mm O.D. and the groove around the insulator accommodates that size. I made the dimensions sloppy enough so that it would slip over the end of a T-post that was buggered up with a hammer. To keep the insulator from sliding down the post, cut a 20 mm long piece of the same tubing and secure it with a cable tie to the inside of the insulator between the two nubs at the desired height. See the photo for clarification. The cable tie also keeps the wire in place when stretching the fence. This insulator is designed to fit a standard 1.25 lb/ft T-post. I modeled a section of T-post before creating the insulator so I included it for your amusement. Please note that T-post dimensions vary by manufacturer.