Hermione could cast the appropriate charms in her sleep after months of camping with Harry. The challenge was keeping the spell to a smaller area. They weren't needing to erect a tent or do anything that required a large perimeter after all. "Done," she said, flashing her eyebrows. It didn't look any different on the inside but no one could see in.
She fished the necklace out from under her clothes and wrap. "Can you get the clasp for me or hold my hair while I do it?" It was too windy for her to manage both without her hair tangling in the thing.