[Lynn Eades]

Hi James here is a picture of two versions of U.C.MkI firing rests. you can see the remains of the rubber strap from one. The strap comes over the gun and is then pulled down onto a stud. the strap has holes in it for this purpose. Im not sure why this was better than the proper mounts that are found around the rest of the MkI U.C. except that the rubber rest was "universal" in that a variety of weapons could be fired from the rest.
I couldn't tell what was involved with the Boys in that photo.