We know now, for absolute certain, that the Jackson and Beers photo were different takes of the Oswald shooting. But, did they mark the floor with chalk to show people where to stand? The Wizard Who's With Us found what appears to be a chalk mark around the foot of Tom Petit in the Jackson photo.
Here it is close up:
"OK, now you stand here, Mr. Petit. There, that's good. Now, raise the mic a little higher. A little more. That's it. Perfect, perfect. Now, just hold that position."