Today it’s all digital. Simple as sending a file.
Prior to that you’d get cans of 35mm film (or sometimes 70mm) that would be laid out in gigantic platters and fed through a projector. Trailers would have to get manually spliced in – which wasn’t terrible hard, just time consuming.
I still have a bunch of trailers I kept from my time working at a theatre back in the late 1990s. Star Wars, Blair Witch, Fight Club, and a bunch of others. They’re not really valuable, but man they’re kind of cool to hold on to.
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