Common Room
The Hufflepuff common room is entered from the same corridor as the Hogwarts kitchens. Proceeding past the large still life that forms the entrance to the latter, a pile of large barrels is to be found stacked in a shadowy stone recess on the right-hand side of the corridor. The barrel two from the bottom, middle of the second row, will open if tapped in the rhythm of ‘Helga Hufflepuff’. As a security device to repel non-Hufflepuffs, tapping on the wrong barrel, or tapping the incorrect number of times, results in one of the other lids bursting off and drenching the interloper in vinegar.
hufflepuff
Hufflepuff is one of the four Houses of Hogwarts School of Witchcraft and Wizardry. Its founder was the medieval witch Helga Hufflepuff. Hufflepuff is the most inclusive among the four houses; valuing hard work, dedication, patience, loyalty, and fair play rather than a particular aptitude in its members. The emblematic animal is a badger, and yellow and black are its colours.

House Ghost: the Fat Friar.
"Hope to see you in Hufflepuff! My old house, you know."
—The Fat Friar to the first-years before the Sorting ceremony