No: HPFGUIDX 43498 In GoF page 408 (UK hardb.) Snape says he seals his office with a spell none but a wizard could break. But in her second year Hermione steals Boomslang skin from his private stores, and I don't remember there being a problem with breaking a seal. She just sneaks in there quickly when the others are at potions class. "fruhu"