I'm having difficulty rigging a simple chinese takeout box to have it fold up from a flat plane. Specifically the convex parts that fold inside the main four walls that make up the container. I feel like I need to connect these joints to the bones that make up the main four sides of the container, but there doesn't seem to be any way to connect or join the ends of a joint chain. Is there a solution for this seemingly simply problem?
Have you tried making it as an IK-chain and put the goal as a child of the bone you want it being connected to. Better yet set the bone as your goal in the IK-chain.
You can also try using what i think is called a constraint or something alike. It can bind the movement of one object to another. You can find it if you right click and look under motion at least in R13 student.
If everything else fails you can always complicate things with the use of espresso.