Structure Placers have the same texture as paper and are used to spawn the 4 types of main generated structures from Project Zulu. They were created initially for map-makers or just testing them out in creative, thus they have no crafting recipe. Holding down right click with one in hand gives a stretching out animation similar to charging up with a bow, and it then spawns the structure with the middle at the cursor location. The four types include:

Oasis Structure Placer: Spawns in a small pool of water with palm trees leaning over it in a grass circle.

Pyramid Structure Placer: Spawns a 50 by 50 base sandstone pyramid that spawns with a maze of tunnels with spawners and mimic chests.

Labyrinth Structure Placer: Creates a big labyrinth of tunnels with spawners, mimic chests, and haunted armor that comes out of the ground as you get close

Graveyard Structure Placer: Creates a square plot surrounded by a broken-up cobblestone wall with blank Tombstones scattered inside and a small stone brick structure with a loot chest inside.