Something I did when I fed live is watch if the snake didn't constrict the rat properly enough, maybe front claws or hind claws are hanging out too much and can scratch at the snake- I just use the tongs to hold their feet to prevent that.
Occasionally, the snake would constrict poorly, and the rat's whole head is loose and free to bite the snake. It's not pretty, but I hold their mouth/head off with the tongs to prevent bites too, so they end up chomping on the tongs instead of the snake.