They were plastic. They used to hold water. I've never seen those in glass. Moving them you had to pull it little sideways and roll it on the bottom edge.
Back in the day, those water cooler jugs (carboys) were made of glass but for many years now they have been made of plastic. The glass ones are coveted by homebrewers because they don't scratch and harbor bacteria. Sorry for the OT tangent, I've got a few in the basement I got from the local bottled water outfit about 25 years ago.