Perfect Square Piece Uniform Pattern Strong Light Square Clean Edges nasty thing. I have found that 400 or 600 grit sandpaper works well to break up the edges without rounding the edges too much. If you need to sand any contours / fill the container with water, add a drop or two of dish soap and leave the sandpaper in the water for a few minutes. This makes the sandpaper less hard and makes it easier to sand cutouts, corners, etc. I have successfully used CA glue (superglue) to glue the parts together. The places I glued, cleaned with sandpaper, cleaned of dust, etc.