Talon rat bait. It can come in small blocks that I have used by screwing through them onto a timber post. Worked a treat. If you screw them down the rat can't take them away. It eats enough to kill them and leaves some for the next rat. A good ratter dog can also help. Cats tend to catch only one at a time for food. A good dog will kill and keep looking for more.
In the days I had the problem I was also an agent for Golden Fleece Petroleum.
