Thats what i get for typing to quick , Im referring to His Pyramid .
say what
Gaara's pyramid is a more advanced form of Sand Burial. By itself it is not a sealing technique. He uses it in conjunction with sealing tags or another sealing technique in order to seal an individual within the pyramid prison.
You're not missing anything, it's as simple as it looks. Sealing tags are infused with his sand, and anything bound within the sand can be sealed. It doesn't need to be a pyramid to work, but the pyramid helps keep whatever is inside under more pressure, thus increasing it's chance of success.