This is a chalk holder made to resemble a lightsaber. The chalk goes where the laser blade should be and the knob holds it by means of a screw. You may use color chalks to make it more realistic.Print both parts and join them with a screw. I recommend to download the source code and look for a parameter called 'screw', and 'r_screw' for the knob, since those are the values for the diameter of the screw that is going to be used. By default both are 3 mm.