Sherlock gives a hum of agreement, just enough dubiousness in it to express his feelings on the matter of the spell itself, as though they weren't already clear, and lobs another book over his shoulder.

"Suppose there's always the risk of someone hearing," he owns. "A chance. Not too likely. Not today."

Weekends most people keep to the lower levels or the common rooms, studying or lounging about with mates or other similarly dull activities. Mostly dull. The latter has its place, at least when that mate is John.

This is still better. Will be all the more so once they're done clearing space. The next book gets hardly a glance before it's sent flying.

"Perhaps we're practicing repelling charms." They can certainly say so, if asked.