This is a trailer made from a $10 garage-sale bike, sawed in half. Everything's bolted together--no welding. The real wheel from the original bike rolls backwards relative to the direction it rolled when the bike was intact. That means that the freewheel doesn't freewheel, and the pedal goes around, warning drivers to leave plenty of space.
Other features include a locking hitch and a locking lid on the box. The one problem is that the center of gravity is too high and it's easy to roll the trailer.
I made this about 20 years ago. Sorry I don't have more pictures. The headset is still intact, hidden in this picture, joining the fork that holds the right (formerly front) wheel to the top and down tubes which are now supports under the box.