Magnets Getting the strength right is key. I used neodymium magnets, they are stronger for their size than ferrite magnets and less brittle too. Around a 3-5kg pull strength is ample. https://www.first4magnets.com/circular-disc-rod-c34/20mm-dia-x-3mm-thick-n42-neodymium-magnet-4-6kg-pull-p3300#ps_0_3352|ps_1_1481 Backing Board Any magnet (ferrous) material. I used a piece of metal sheet I got from our Blacksmith neighbours. You can get steel