I stopped by my local supermarket today after work to pick up a couple of things, and brought one of my 10,000 cloth grocery bags along. I purchased the following: apples, oranges, cereal, lettuce, cottage cheese, pistachios and a bottle of wine.
After standing on line for at least 10 minutes, I unload my purchases on the conveyor belt thing and place the cloth bag on top. This is the universal sign for "put my stuff in this bag, please."
Cantankerous Cashier: Hi.
K: How are you?
CC: I've been a lot better.
K: *awkward silence*
CC: Is this your bag?
K: Yes, it is.
CC: Are you planning on putting your stuff in it?
K: Uh -- yeah, I can put everything in there when you're finished.
So I run my debit card through and walk to the end of the still-running belt thingy, where she had tossed my bag along with my groceries. She stands there and watches me bag my purchases before she starts checking anyone else out, and then she hands my receipt to the next woman in line.