They used to float around the internet around 5 years ago but i can't seem to find them again.
Now that you work for the municipality and have your high-vis vest for safety on the streets, look at the side of the panel. There is a hex-shaped hole for an Allen Key. From where you are facing in this photo, it should be on your right.
Bring your Allen Key, twist it open, raise the glass, put in your ad, lower the glass, tighten the Allen Key.
