isnt it easy to build a mill from scratch!!
look at their site and u can kinda get a basic idea of how to put it together. quickly tho, sorry dont have too much time tonight.: its a simple like 2'x5' piece of particle board framed up by 2x4. tight on the edges and about 6 inches on both ends left open between the frame and the particle board. 2 rollers (similar to the old school roller treadmills) (1 at each end) are secured in the open spaces of the frame. attach short legs at the front for the incline, carpet mills need an incline, im not sure on the degrees, i wouldnt go too hight, but u can probably find out if u search online. or email grand carpet mill and ask their incline. then secure another 2x4 frame, (an upside down "U") to the first frame to use as a brace to attach your dogs harness to. the one i have is not carpet, its a rubber mat that is fastened together to make the belt. its feels extremely durable and tough, but soft enought for them to walk on. the particle board u use should be laminated on atleast one side (up side) for the belt to slide on. also mine is not pulled tight (no tension) and thats good for roman just starting out. roman hates the frame that secures his harness tho. so i take it out and just use a leash. i hope that helps, heres a few pics.
heres some pics of a mill
saw this on another site!! thought ud like the pics man for reference