We recently took over a retail outlet and needed a method to hang signs from the ceiling. IF we could even find them, these clips were ridiculously expensive.
While having lunch at Timmy's (Tim Hortons) I had a distant glance at what they used to advertise their donut special. My blurry cell phone photo showed me something like this, and after some contemplation and discussion in the R&D department, we came up with this. Two iterations later, success!
Due to the required flexibility of these clips (to open it), ABS is the recommended material. PLA is too rigid and brittle.
Pinch to open, slide over the 1" T-bar rail, and let it go. Done!
We used the lulzbot mini on medium settings with a 0.5mm nozzle, 4 walls, and 8 solid layers for top and bottom.