Detail of one of the holddown posts (visible behind the nearly-horizonal blue
strut) in the S-IC's thrust structure (this particular holddown post is painted
black and is on the unlit side of the S-IC, making it more difficult to see).
Picture 2 of 2.
The entire Saturn V rested on four of these holddown posts on the pad.
Hold-down arms on the mobile launcher also clamped the Saturn V to the pad via
these holddown posts as the S-IC's five F-1
engines built up thrust after ignition and released the Saturn V once all
of the engines were up to full thrust.