Specialized tool for adjusting lighting fixtures. Made of cast aluminum, and available from any Altman dealer, MSRP $9. Web link. Most useful for locking down the Tee handles locking the tilt, fits most other manufacturers' units as well as those of Altman. Possibly originally made by Century Lighting, and therefore known as a Century Wrench, but this has yet to be proven.
Due to the resemblance to a crucifix, also known as a "Dracula Wrench" or "Jesus Wrench."
Various vendors could, on special order, put their custom logo in the quarter sized circle just above the 1/2" square opening; thus it can also be called a Bash wrench, Production Arts wrench, Oleson wrench, etc.
Ironically, Altman calls it a "Stagehand Wrench."