Mr. Shelley (or some other member of the flooring crew [internal OR external] who is in on the plot) sees Mr. Oswald, in the course of his order-filling duties, touching a box on six, before the internal crew take their lunch break. He takes note of the box. This box is later singled out and brought to the SN window (by a conspirator wearing gloves) and placed there to incriminate Mr. Oswald.
**
CAPTAIN FRITZ: Okay, Lee, have you ever seen this sack before? Here, take a good look at it before you answer.
**
See how easy this is?
And what makes it so easy is the abject inability of the Warren Gullibles to place
-------------a sufficiently lengthy package in Mr. Oswald's hands that morning
-------------Mr. Oswald at the SN window at 12.30pm that day