Director Hal Ashby must have identified with Alfred Hitchcock's occasional penchant to slip an event into his movies that completely defied logical explanation, what Hitchcock termed a MacGuffin, because he did the same in this scene where Harold and Maude carry out a plan to dissuade Uncle Victor from taking him into the Army. (Check out this classic MacGuffin in Vertigo)
Then ... "Rat-tat-tat" ... to convey the excitement of battle to Harold, Uncle Victor takes him to the ruins of Sutro Baths where he fervently re-enacts the firefight that cost him his right arm.
... and Now, this was filmed next to Shipwreck Point, the plateaued area at Point Lobos (map) whence over the decades the curious looked out to many a doomed ship. The rock face constantly weathers and erodes but its cracks and contours can still be matched up with the image above.
... circa 1937 ... Here's a vintage aerial of such a shipwreck, the Ohioan - an arrow points to the plateau. City history buffs will appreciate the excellent perspective of Sutro Baths as it was and Cliff House at bottom center as it still is. Note too at left the rip-rapped masonry wall bridging out to Fishermans Rock. It was removed in the 1980s after one too many fishermen was swept to his death by errant waves.
... and Now, the only reminder of the magnificent Baths complex - it burned down in 1966 - are the skeletal foundations, still looking much as Harold and Maude experienced them.
Then ... Harold becomes uncontrollably animated, savoring (paraphrasing his words), "the thrill of the kill, the bayonet, the slitting of throats!" - Uncle Victor is growing increasingly alarmed - "souvenirs of privates, of scalps!" ... Just then Harold spots a war-protester waving a peace sign (Maude) and rushes over, loudly berating her as a traitor and a commie pig.
... and Now, Shipwreck Point still looks the same. The pedestal and embedded metal anchors at left are remnants of the terminus of the short-lived sky tram that ran from here to the Cliff House from 1955 to 1965.
This vintage photo shows the Sky Tram approaching the Shipwreck Point terminus. The waterfall flowing beneath it, pumped from the ocean below, was an added attraction for the tourists.
Then ... Harold grabs the sign, brandishing it over his head while he chases Maude across the plateau and down a set of steps (visible in the image above), closely followed by Uncle Victor waving his good arm in a futile attempt to calm the lad down.
... and Now, the steps have slowly deteriorated into a dangerous state, now off-limits to visitors.
Then ... There's a terrace at the bottom of the steps.
... and Now, CitySleuth risked life and limb to get the matching shot. Note that the hole penetrating the rocks at left has been filled in for safety's sake.
Then ... A scuffle ensues in a walled corner of the terrace. That open drain by their feet is about to play its part in the MacGuffin.
... and Now, this part of the lower deck has crumbled away; click or tap the image to superimpose it, showing exactly where it was.
With a whoosh and a splash Maude suddenly plummets down the drain. Uncle Victor, horrified, peers into the dark hole...
... but all he can see is his reflection rippling within the surface of the water. "What Have You Done?!", he screams. Maude is gone; how she ever survived is left to our imagination, and the ruse has worked ... Harold is off the hook.