When I saw her I shouted "HEY!" Her tail flicked between her legs and she came charging back through the gate, her straight line only interrupted by a wide circle around me "BADDOG!" I shouted. "BADDOG!". She jumped onto the GOODDOG chair and tried to look like a GOODDOG, but I was pretty cranky with her. I needed something to hit her, but there were no small sticks or blades of grass handy. Of course there were rakes, broom handles, power cords and large branches lying around, but they would hurt her. I didn't want to hurt her, just BADDOG her.
The only thing at hand was a 0.5m x 1m sheet of light cardboard. I grabbed that and rolled it into a tube. Polly realised she was a BADDOG and hid in her kennel where I couldn't reach her.
She stayed in there for an hour until I fed her and gave her a pat. She knows she's not allowed out the front. Cattle dogs have a reputation for being bitey, and if she's running loose someone will call the pound about a dangerous dog running free. I had to put the fear of cardboard into her. Hopefully she'll remember that the next time the gate is open.