I made this Big Mac Knex Truck. After the back door is opened, it makes way for storage. I used it to store my hot wheels. Furthermore, the roof can open. In addition to that, the hood can be opened to reveal a hollow space where the driver is supposed to be. That's where I'll be putting a motor in later on. The trailer obviously can detach from the truck. It's the only one on instructables so I'll be posting instructions as soon as possible. Rate and comment! Enjoy!