The sign accompanying the holddown arm. It reads
Saturn IB Hold Down Arm
Getting History Off the Ground
No one has ever counted the number of technical challenges we needed to
overcome in the infant days of America's space program. Many of the early
rockets would lift just a few feet off their launch platforms before falling
back in an explosion of fuel.
As obvious as it seems now, these early failures demonstrated the need to hold
the bigger rockets on the platform until the liquid fuel engines could build up
enough thrust to safely lift off.
This Hold Down Arm is one of eight of these devices -- one under
each of the Saturn IB's fins -- that held the giant rocket in place during
these critical seconds. The entire weight of the rocket was supported by the
Hold Down Arms and secured only by the hooks (painted yellow for easy
An explosive release device in each arm was electrically activated when maximum
thrust was achieved. The arms served also to hold the rocket in place during
transport to the launch pad and in high wind conditions.
Note: Most documentation I have read uses "holddown" (one word) vs. "hold
down" (two words), but I transcribed the sign as it was written.