This is a simple clip design that i made up to help with gluing LEDs into Light boxes but i have since found many uses for it, there's 2 sizes available a thin and a thick version, use the scale setting in your slicer software to adjust the sizing to your needs  

Default sizing is:
Thin (clip.step) -  4.5mm gap x 40mm long (gap) with 3mm/5mm thick legs
Thick (clip2.step) 4mm gap x 40mm long (gap) with 8mm/8mm thick legs