Enchanting sets of items

The corebook is -- perhaps on purpose -- somewhat vague about what can be enchanted.
One thing that is not entirely clear from it is whether a set of items can be enchanted as a single device.

For example, in many folk tales, the hero receives a pair of magic boots granting anything from stealth to fast transportation to mountain-kicking prowess. One could imagine that an Hermetic magus would enchant only one boot, but that feels wrong. And obviously, it would be stupid to enchant separately each of the two boots with the effects you want to bestow on the wearer. Because of this, and because the corebook does not really say otherwise, we assume any set of items that are meant to be used mostly together can be enchanted as a single device. If the different components are not used together, the device does not work. Examples include a pair of boots, a horse tack, a lock and its key(s), a pot and its lid, a chessboard and its pieces etc.
How about your games?

Another good example of this is a spell like Hardness of Adamantine, which considers an entire suit of armor to be Target: Individual.

There is thankfully a convenient in-universe explanation for this. I would consider a pair of shoes to be sympathetically linked enough to be enchanted as one item, but only if they were created as a pair; if you originally had two pairs of the same type of shoe and lost one from each pair, you couldn't enchant the two remaining shoes as a pair even if you could use them as such. That's a lot more nit picky than most games would ever have a chance of noticing, though, so it's basically irrelevant. More relevantly, a magus could choose to make it work either way; he could enchant a pair of shoes, or if he had some special reason to, he might only enchant one, or enchant one more than the other, but this would make the enchanting of the shoes a separated process.