Tea Kettle

After performing a fūinjutsu, Gaara can seal the target inside the item, otherwise, it can be possible that the target itself choose willingly to get inside it, and after that, he apply a sealing tag to prevent the chakra sensing of the target.

Influence
The tea kettle is likely a reference to the Japanese fairy tale Bunbuku Chagama, whose story tells about a tea kettle which transforms to a tanuki, the latter is likely a reference to Shukaku.