Haversacking

Haversacking is a widely used, though unofficial, term for the magical practice of using an Undetectable Extension Charm to vastly increase the internal storage capacity of a container, typically a bag, without altering its external dimensions or weight. This advanced piece of magic allows a witch or wizard to carry a seemingly impossible number of items within a small space. The most famous application of this charm is Hermione Granger's beaded handbag, which was essential to the survival of the Trio during their hunt for the Horcruxes.

While “Haversacking” is the name of the practice, the core magic involved is the Undetectable Extension Charm.

• Incantation: Unknown. The incantation for the Undetectable Extension Charm is never stated in the novels.
• Pronunciation: Not applicable.
• Wand Movement: Unknown.
• Light: None described.
• Effect: To magically expand the internal dimensions of a space or container to a significant degree. The exterior of the object remains unchanged in size, and its weight is not affected by the additional contents. This makes the charm ideal for transportation and concealment.
• Type: Charm.

The principle of magically expanding space has been used on various objects throughout the series, but the term “Haversacking” is most closely associated with its use on bags.

• Hermione Granger's Beaded Handbag: In preparation for the hunt for Voldemort's Horcruxes, Hermione Granger skilfully applied an Undetectable Extension Charm to her small, purple, beaded handbag. This act was crucial, allowing her to carry everything she, Harry Potter, and Ron Weasley might need. The bag's contents included:
  • Multiple changes of clothes for all three of them.
  • A vast collection of books, including titles on Horcruxes.
  • Essential potions and ingredients, such as Essence of Dittany and Polyjuice Potion.
  • The Peruvian Instant Darkness Powder used during their escape from the Ministry of Magic.
  • The large tent they used for shelter.
  • Salazar Slytherin's Locket and later, the Sword of Gryffindor.
• The Weasley Family Ford Anglia: Arthur Weasley performed a similar charm on his family's car, allowing it to comfortably seat eight people, six large trunks, two owls, and a rat for the journey to King's Cross Station.
• Alastor Moody's Magical Trunk: A far more complex and powerful example of this magic was Alastor Moody's trunk. It contained seven different compartments, each with a unique purpose, including one that was a ten-foot-deep cellar where the real Moody was imprisoned by Barty Crouch Jr..
• Ministry of Magic Regulations: Arthur Weasley once warned his sons, Fred and George Weasley, that using such charms on their pockets to smuggle out joke products was illegal. This implies that the Ministry of Magic heavily regulates the use of extension charms, likely to prevent their use in circumventing Muggle customs or for other illicit purposes.

• Learning: The Undetectable Extension Charm appears to be a difficult piece of magic, as evidenced by the strict Ministry of Magic regulations surrounding its use. Hermione Granger managed to cast it successfully before her seventeenth birthday, a testament to her exceptional magical talent. The illegality of its use on personal containers suggests that it is not taught as part of the standard Hogwarts curriculum.
• Counter-Spells: There are no known counter-spells or incantations to reverse an Undetectable Extension Charm. The primary way to detect its use is through other magical means of inspection