The fourth day's program (March 6) was for Schweickart to exit the hatch on the LM and make his way along the outside of the spacecraft to the CM's hatch, where Scott would stand by to assist, demonstrating that this could be done in the event of an emergency. Schweickart was to wear the life support backpack, or PLSS, to be worn on the lunar surface EVAs. This was the only EVA scheduled before the lunar landing, and thus the only opportunity to test the PLSS in space. McDivitt initially canceled the EVA due to Schweickart's condition, but with the lunar module pilot feeling better, decided to allow him to exit the LM, and once he was there, to move around the LM's exterior using handholds. Scott stood in the CM's hatch; both men photographed each other and retrieved experiments from the exterior of their vehicles. Schweickart found moving around easier than it had been in simulations; both he and Scott were confident that Schweickart could have completed the exterior transfer if called upon to do so, but considered it unnecessary. During the EVA, Schweickart used the call sign "Red Rover", a nod to the color of his hair.