9, In ​​order to make this pentagon look positive, I draw another figure larger than this pentagon, and once again intersect with this pentagon, so that I get a stable pentagon;
10, Next step: Make the thickness of the box, this is 76mm, in order to get the accurate side length, I copied a copy of the pentagon in situ, and pulled out the extra points and deleted it;
11, then copy this side by a distance of 76mm, and use a pen to connect the two lines to form a quadrilateral;
(to be continued)