Knob for Magnet

I have some small strong magnets (like these: http://www.crazy-magnet.de/en/products/3::25/10x-disc-magnet-%C3%98-6-x-2-mm-nickel-plated-strength-ca.-680-g) that are much better in holding paper on a white board than conventional magnets. Their disadvantage is, that they are too small to grip them when they stick to the white board. So I designed a knob for them.