Explosive Knots
Explosive Knots are an example of sufficiently-advanced technology, at least from the point of view of primitives still mired in pre-starflight cultures. It’s not really their fault; at that level of savagery many of them don’t even understand the concept of space-time, let alone how to manipulate it with a piece of string and some manual dexterity. Calling it ‘magic’ at least allows some of the marginally brighter ones to conceptualize the idea of of Explosive Knots, which is really quite admirable of the pig-ignorant brutes.