Coldwaterjohn's photos with the keyword: a

G-Clamp with two 1/4 20 threaded screws welded to its two clear outer surfaces, on to which is attached a Leitz Wetzlar swivel mount. Can be mounted to a fence-post, a branch - as demonstrated here, or any other suitable, stable surface. These were made by my father in the 1930s, and still do an excellent job!