Black water tank valve

A few years ago I had that problem. I actually used a rubber hammer on the handle to close the valve but then managed to open it up again. We were 2000 miles from home. I went to an RV place where we were and they said the whole valve had to be replaces but it would take 10 days to get the valve there. I said no, thanks as we would be on our way home by then. I bought an end of line valve, put it on and used that until we got home. Took the 5er to my RV place and they told me it wasn`t the valve. It was the cable itself that was inside a sheath and was binding. They replaced the cable which was extremely long and it is still working. I did have to get the gray water cable replaced with a rod and found out that the valves all face the door side of the trailer and not the side where the push/pull handles are. Makes sense to me....Anyway they managed to twist the gray water valve so it faced the right way and now the rod works good. There is a way to lubricate the cable inside the sheath but I can't remember the name of the part.