In reprinting your negative with a shadowgraph border, you first insert the negative into the enlarger film carrier and project the image on the easel. With the red safety filter in position, place the printing paper on the easel and lay your shaving props directly on the printing paper, arranging them in neat order around the center of interest. Expose for one-third the normal time after which, without moving the paper, shift the positions of the razor blades slightly, and then expose for the second third of the normal time. The last third of the exposure is given with all the props removed from the paper.
Sadly (not maybe not), in the modern world of photography adding ghostly paper clips and razor blades to photos is no longer in vogue. Check out the full article here with more example photos.