|Muggles' Guide to Harry Potter - Magic|
|Features||Seals a door|
|First Appearance||Harry Potter and the Order of the Phoenix|
Colloportus seals a door.
We first see this spell used at the Battle at the Ministry of Magic where Hermione, Luna, and Harry are using it to seal doors against the following Death Eaters. While it does seem proof against the unlocking spell, the effort is ultimately insufficient as there are too many doors that have to be sealed.