I'm posting this in response to a recent ICON discussion regarding these solid glass legs that frequently appear as a topic of debate. Some feel they are glass sidewalk prisms, glass battery rest insulators, or electrical apparatus platform legs.
I obtained a set of these (4 glass legs) at an antique shop in the Mojave Desert a few years ago. They consist of two well manufactured pieces of channel iron, with one pair of the glass 'legs' mounted at opposing ends on each. The iron channel was clearly painted at one time. The channel is capped at each end. The glass 'legs' are each held in place against the end caps with a metal dowel that snugly fits into a side groove that is incorporated into the glass legs. The metal dowel is secured with two slotted screws that thread into the metal dowel from each side. It is rather obvious that this was originally manufactured for a specific purpose, not a secondhand creation by someone for re-purposing.
I have this pair mounted to a fence among many other industrial rust objects, so I apologize for the crude angular photos. The left pic exhibits the two units hanging horizontal against the fence. The one in the foreground is a bit obscured, but the one in the background can be better seen in its entirety with the 'view original' feature in the header above. The other two pics show how the glass legs are securely mounted at each end of the channel iron. All of the legs have some high-point wear on the bottoms.
I have also acquired these glass legs with raised male threading molded into the larger end. The glass has been found in clear, light sca and deep purple. They were likely made of clear glass containing manganese, with many 'purpling' upon UV exposure.
It is this poster's theory that those like the set here were used as insulating legs on platforms for some form of electrical or medical apparatus. A battery bank platform is also a possibility, but the use of metal in combination with battery acids creates some question? I am quite confident they are not glass vault lights (prisms). Hopefully a patent, or some form of absolute documentation will appear someday.