I actually just had to do this the other day. My neighbor came to me with a dekays snake that was badly injured, he hit her while mowing the lawn and felt bad (he didn't see her). She was really gashed up, missing the last third of her body and cut up but probably would have lived like that for at least a day. So I too had to do the same... And I still employ the brick method. I lay the brick on my driveway and then place the snakes head under the edge of it, and then I stomp on the brick. That way, there is no accidental missing or hitting the snake only halfway and injuring it more. It's about the quickest way to ensure instant brain destruction which is the only way to end suffering. I have been thinking about it all week... It eats at me every time I have to do it. But I know that her fate was sealed and that in all reality it was only a matter of time, and I shortened how long she had to suffer.