The small tubes on the bottom are to support the printer when closing the hole. 2mm hole depth to avoid scratching out the spider web when printing into the air without support. If you do not want to drill holes into the wall, this might be a solution to mount the base of the vitoconnect 100 to any tube with 110 mm diameter and then snap the device onto it. I mounted it to an isolated heating system tube, using this 'adapter'. You have to lay it flat on the printer table, so rotate before printing.