This thread about the construction of the rifle rest has given a new understanding to what LHO was doing between the departure of the floor laying crew and the arrival of BRW. A big question is what LHO would have done if BRW had actually gone over to where LHO was sitting. Would he have decided to not shoot at JFK or just killed BRW.
Of course any answer would just be conjecture. But my theory on it is this. There is credible evidence, in my opinion, from Arnold Rowland of seeing someone who resembled LHO with a rifle at the west end of the sixth floor for no more than 30-seconds sometime around 12:15 but no later than about 12:25. So my much earlier opinion that LHO was sitting in the sniper’s nest the whole time BRW was eating his lunch seems questionable.
It appears to me that LHO probably went to the west end of the sixth floor, shortly after Givens left, to retrieve his rifle that he hid there that morning. Before he could take the rifle back to the already prepared sniper’s nest, BRW came up to the sixth floor and ate his lunch. LHO stayed quiet and out of sight near the stairwell on the sixth floor. If BRW had come over that way LHO could have left via the stairs. When the sounds of the ambulance arrival happened LHO probably felt the need to find out if that was the motorcade arriving. If it had been the motorcade, LHO could have fired shots from the west window before anyone could stop him. However, once BRW left, LHO was able to go to the sniper’s nest in the SE corner as he originally planned.
If the above is wrong, and LHO actually was in the sniper’s nest the whole time, and BRW had come over there and had seen him, he could have simply said he was waiting to see the motorcade. This is provided his rifle was not in the line of sight of BRW. Perhaps the rifle was on the floor against the tall stack of boxes, this would be out of sight of anyone not inside the tiny sniper’s nest but close enough for LHO to grab it when needed. I don’t see any scenario where LHO would kill BRW before the motorcade arrived. That would create too much noise and draw unwanted attention which would cause an abortiion of the assassination anyway.