Attachment to use the standard utility knife blade as the algae scraper. Holes are made to be tapped. Make sure you have enough perimeter thickness to support the tapping. I printed with a .80 nozzle and 1.6mm perimeter thick, You need a couple 1/4-20 nylon thumb screws. Or any nylon 1/4 screws you can pick-up a lowes Print and use super-glue to attach to algea magnet. Print so the smooth side is the glue surface. Have to flip STL. Use at your own risk. Blade is sharp.