Sealing wax is a malleable material which, after melting, quickly hardens (onto paper, parchment, ribbons and wire, and other material) forming a bond that is difficult to separate without noticeable tampering. Sealing wax is primarily used to seal envelopes or documents. Hogwarts acceptance letters were closed with a purple wax seal bearing a large "H" and the four animals representing the four Hogwarts Houses.