SnapFit
thingiverse
Did this a while ago. Worked pretty well, used 4 to hold a 3/4" wood "wall". There you have an .stp file if you want to do some modifications.
Download Model from thingiverse
With this file you will be able to print SnapFit with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on SnapFit.