Construct a treadmill to exercise your pet! Assemble 2×4 boards into the treadmill frame and cover the top of the platform with a piece of plywood. Fit a block of wood into a PVC pipe for each axle, drill a hole through the wood block and attach the axles on a metal rod to either end of the dog treadmill. Cut a length of carpet to encircle the treadmill and sew the ends of the carpet together. Attach a metal bar to the top of the platform for added stability and use cinder blocks to elevate the platform or attach wood blocks to the treadmill for legs.