This is the car familiar you saw the blind lab running on. I took the pulley out so I can show you the frame. It's made out of two by fours. Pretty simple. The only thing right here that you want to keep in mind is the size of your dog. I want to make sure that it's long enough for him to run on without running out the front of the back. The top up here is made out of thin plywood. You don't need anything real heavy just that thin plywood is all you need. The axle is a 4-inch PVC pipe. I've got a piece of landscaping timber inside. You can see it doesn't fit exactly in here. It would just spin by itself. If you didn't take a few of the screws and put them on the side. Just don't tighten it down too tight or else it will wind up being out of round. It doesn't have to be real tight just enough to keep it from spinning freely. This is your bearing. All it is is a piece of copper tubing. I found the diameter of the copper tubing and I just tapped it in with a hammer. That way that just slides in and spins freely. Take your pilot hole that you made. Just run it in there and that way you can find the center easily and hammer it in. The only thing with this is that you have to keep in mind that you want to see where I experimented with the height of it. You want to have this top leading edge of your pulley above the edge of this running board. For else you will wind up catching it and it will slow your dog down and create friction. You want it to be able to come over and miss this. The carpet just made sure I would have spined the old piece of carpet and measured out the width and the length. And the way I did it, which this is what took the longest on the whole thing. I got 50 pound test from the fishing line and threaded it all the way through all the way down to the bottom. The needle I used, I didn't have anything. So I just found an old spoke off of a bicycle wheel and bent it in a little semi-circular hook like needle. I just used it and just worked it all the way down. And it hasn't come apart and I don't think you'll have any problems with it. As long as your carpet isn't rotten, it will hold together real good. This frame right here is what holds your leash to your harness dog. That's pretty self-explanatory. All it is is 45 degree frame with the pipe going through the top. And I just used some nails to keep them sliding out. You can, if you want to, drill a hole here, put your little eye hook at where you can quick release your leash to your dog. The legs, I use center blocks, but you can just as easily make some legs for them just like this. We just have them down here. If you want to have the front elevated, just a little bit. Depending on how hard you want your dog to work is to how high you elevate it. If you have any questions on anything else, let me know. I'll try to explain it the best I can.