I bought one set for my Jinma and its 5' rotary cutter. Jinma hydraulics were notorious for never staying where they belonged, plus there was no draft control. A pair of slotted brackets attach on either side of the toplink (tractor end). One chain goes on each lift pin (implement end). Raise the hydraulics past your desired cutting height, put the chains in the tractor end slots, lower hydraulics. Nose of mower will never dip lower than the length of the chains. It can go up, but not down.
My KAMA has draft control, but I use the chains anyway. Plus, I had three more sets made up at the local welding shop. I still use the original tractor end brackets, but now have four sets of chains to spread around on my implements. I've used them on rear blades with success, and they were indispensible on the Yanmar's rear PTO driven MMM. I also plan to experiment with them on the box blade and rock rake (although I'm leaning more toward gauge wheels for the rake).
//greg//