These are corner blocks are for the Mostly Printed CNC and are made to be glued together and then screwed into a base plate. There ara 6.5in and 3.5in base risers that pitch out for a sturdier base. The 3in, 2in & 1in blocks can be added as many times as you need for added height. These parts are hollow to conserve filament, but also have the proper internal supports so that the part will come off the printer as designed.