This is "Gamera" a tortoise who needed his front leg amputated because of an injury. Vets at Washington State University's College of Veterinary Medicine amputated his leg and attached a hardware store caster to his lower shell so he would be more mobile after surgery. It's worked great, and Gamera can get around on many surfaces. Here's a story and short video showing him walking on grass. He looks a bit awkward but I'm sure it's much better than being three-legged and he probably does better on dirt. Gamera is only 23 pounds now, but these tortoises can grow very large so he may need a heavy-duty wheel later in life. It's always heart-warming to know that people will use their skills and creativity to give an animal a better life. A $10 wheel from the hardware store gave this tortoise better mobility!