The Customs Sergeant is located in Rimmington in the Customs Office, located at the south end of the town. He plays a minor role in the Rocking Out and Pieces of Hate quests.
During Rocking Out, he has the player arrested under Article 4 of the Maritime Law[1] when his questions to identify whether the player is a pirate are all answered correctly.
After being under the impression that the arrest will help him obtain a promotion,[2] he orders the player to store all their items into the locker so that it may not be used as tools for escape, and also to be processed as evidence by bankers.[3][4]
This article on an NPC has an associated transcript page. Click here for a transcript of possible conversations and other messaging related to this NPC.
The Customs Office where he resides covered up three of the eight willow trees originally south of Rimmington.
There used to be a level 1 Invisible player in the room marked by a yellow dot on the minimap. The "player" could be examined saying: "Invisible Player". This has since been removed.
^Customs Sergeant, "Rocking Out", RuneScape. "Now put all your belongings into that locker as evidence. I can't transport you if you have anything that might help you escape."
^Customs Sergeant, "Rocking Out", RuneScape. "It'll all go into the bank. We can ask bankers to list all the items they think are stolen, ready for your trial."