Started with a Trek Kid's Trailer. Added wooden deck lined with Aluminum rails. Built last weekend to haul my tools around. I used tie up a Tool Chest with Wheels behind me. Rode that till the wheels literally fell off. I had made another trailer from a shopping cart and wheelchair. A bit heavy and tracking was off. Decided to try a single wheel trailer based on thoughts and ideas garnered from this site (thanks). Seems to be working out ok, so far.
Started with a 24" wheel, but have changed it to a 20".
I want to add electric motor in the future to it.