FWIW snood, when it was Simi's time, I don't know how to explain it, but she told me.
I know all the people here who love their pets can understand that we looked in each others eyes, and something changed in them as she met my gaze, and she told me "I don't want to do this anymore."
She didn't look at me like that any time before in her long life. Wasn't pain or anything, just, "I'm done."
Stood up, called the our vet who is 3 blocks from us, and we went in. They made it a very special and comfortable experience for her.