A mount or bracket for signs, allowing attachment to a t-post using a 1/4" bolt. I used it to attach a wheelchair accessible parking sign. This print requires supports; I recommend tree supports with a “no supports” rule painted on the interior of the threaded area. The pin, at least with my configuration, needed to be glued into place with CA glue. 

Due to strong Kansas winds, I printed this out of Ambrosia Dark Blue ASA-CF filament; I used a .4mm layer height, .82mm width, 3 walls, and 40% 3D honeycomb infill. Other filaments with UV resistance and strong interlayer bonding strength should work well - keep in mind that you may need to tap the bracket into place if the top of your t-post is warped or bent, as it likely will be from being pounded into the ground.