Grandfather clock

A grandfather clock is a clock in a tall, free-standing wooden case, driven by weights.

There was a grandfather clock at 12 Grimmauld Place.

There was also a grandfather clock by the entrance to the Gryffindor common room.

Remus Lupin told his Defence Against the Dark Arts class that he once found a boggart in a grandfather clock - this may have been the grandfather clock at 12 Grimmauld place or by the entrance to the Gryffindor common room.

Appearances
Harry Potter and the Philosopher's Stone

Harry Potter and the Prisoner of Azkaban

Harry Potter and the Order of the Phoenix