I made a cardboard carry box that quickly attaches to a bike rack. It fits on snugly and securely, but can be quickly detached so you can use it for shopping or put it away when not needed. It is entirely cardboard and glue except for the plastic reflector and paint.
This is Part 1, which introduces the bike box. Part 2 shows how to build the parts that connect the box to the bike rack.
https://youtu.be/MyEUeAAhgOo
Cardboard is a great material for this project because it is light in weight and easy to work with. You only need a hobby (X-acto) knife, cardboard, glue, and paper bags for the joint material. The only disadvantage is that it's not waterproof.
