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Detail of the holddown posts (visible behind the nearly-horizonal blue strut) in the S-IC's thrust structure.

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.