“Very simples customizeable compass cutter. The tip holder was designed to fit both a pen or a sharp tip, to draw or cut papper, EVA and other kind of soft materials. i was using with my hobby knife like this one: http://www.aliexpress.com/item/Metal-Handle-Hobby-Knife-cutter-knife-craft-knife-pen-cutter-10pcs-Blade-Knives-set-for-PCB/1868603711.html To lock both knife and the position on the ruller, i attached m2 screws. The ruller is in centimeters”