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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 identification).

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.