I got a big sack of Kold Kutter's a while back. I've added them to boots with soles that had pre-drilled holes and other boots without holes. But only rubber soled boots, not felt. I've just driven them in -- without pre-drilling -- and I imagine that would work with felt too. I have noticed that some boots have softer rubber than others and with softer rubber, the screws tend to fall out during usage. With the softer rubber soles, I added a dap of Gorilla Glue to the screw threads before driving the screw into the sole which seemed to help.