House point hourglasses

The House point hourglasses are located in the Entrance Hall. They record the number of house points that have been awarded or deducted. There are four giant hourglasses; one for each Hogwarts houses (Gryffindor, Hufflepuff, Ravenclaw and Slytherin). During Severus Snape escape from Hogwarts after he killed Albus Dumbledore in 1996, a curse shattered the Gryffindor hourglass, causing red rubies to flood the floor like blood. The Slytherin hourglass was shattered in 1997 during the Battle of Hogwarts and green emeralds rolled across the floor. The two were probably repaired and remounted on the wall.

When points are earned some gems (depending on house colors) fall from the upper bulb into the lower. When points have been deducted, they do the opposite retreating into the upper bulb. The hourglasses can also record negative points, by adding black gems to the houses bulb.

It is worthy to note that when Albus Dumbledore died the Gryffindor hourglass was smashed, symbolizing that Albus Dumbledore, Gryffindor house's greatest member, was dead. However, when Lord Voldemort was defeated it was the Slytherin Hourglass that was shattered to show the death of Tom Riddle, Slytherin's greatest member.

Behind the scenes

 * In the video game adaptations of Philosopher's Stone, Chamber of Secrets and Prisoner of Azkaban, they are located in the Entrance Hall on either side of the door leading to the grounds.
 * In both the film and video game adaptations of Order of the Phoenix and Half-Blood Prince, the Hourglasses are located in the Great Hall to the right of the staff table.