These screws are studs that you should screw into plastic washers / pads glued on the back of the letters. 3″ is the standard screw length that our installer uses for the letter installation. I’ve sent you all the parts you need for the letter installation – letters themselves, plastic template with printed letter pattern and metal screws (studs) that you need to screw into the washers on the letter backs. No parts are missing. Sorry for the misunderstanding.