As TopNotch said, back in the day when you could dock pups yourself people would do it with a clean razor, it was usually done within the first 3 days of the pups being born, trying to do them after that with a blade could lead to problems. When done properly the pups didn't go through any pain, The process was fast and the pups were given back to the Dam who cleaned them up.
I also seen tails docked with lamb rings many years back on pups that were too old to have them docked with a blade. The ring was put on the tail, after a few days tail went limp, lost a bit of hair, went a purple blu