Anti-pet doorknob

Warning! Do not use if you have a destructive pet. Design contains small metal parts that could hurt the animal.

This is a simple model I made to prevent my dog from escaping the house. Octagonal shape is a bit easier to grip than round, especially for children.

Fits on 8mm square spindle, uses 3x10mm screw and drop-in nut to secure it. No supports needed.