Abstract: A trailer apparatus is provided having two half forms connected to a frame joint, the half forms mounted on a first and second pivot bar on the joint frame to pivot to open and to pivot to close in a clam shell arrangement. The trailer apparatus may assume a form of backpack or luggage piece adapted to store items and may assume the form of a towable trailer, having a tow bar, wheels, and a three-dimensional covering over the open sides of the half forms to enclose cargo space or to keep a pet inside the footprint of the half form adapted as trailer bed when the trailer apparatus is extended for use.