Barbury Castle Tetrahedron
From The Crop Circle Ship Wiki
The Tetrahedron at Barbury Castle from the 17th of July 1991. It is expected that this design incorporates, along with the Watersphere itself, the three main componenets of the crop circle ship which are required to provide the working energy system.
 Watersphere in the tetrahedron
A common symbol for the Watersphere and its 3 main layers is shown below.
 Object 1: Microwaves
This symbol can be identified as Microwaves. The 6 curves in this design may represent the 6 spherical cavities (S1 * 3, S2 * 3) that the Microwaves pass through before reaching the object in the center of the Large Tetrahedron Structure, the Watersphere. Below, the 6 microwave cavities are shaded in red.
Another (or possibly the primary) reason for the six curves is to represent the Wave Guide.
Chris Hardeman demonstrated this in his model of the Large Tetrahedron Structure in the Gravity Shielding Experiment. Additional evidence for the presence of this Wave Guide may exist, including the 1995 formation below showing Microwaves in a specific pattern.
 Object 2: Microwave Cavities
This second symbol represents an empty cavity through which the Microwaves travel.
 Object 3: Electrical Structures
Designs of the Electrical Structures show the connection and interactions of themselves with the Watersphere. This corner of the tetrahedron formation (image above) shows us that connection again, the Electrical Structures and the Watersphere at the center of the formation.
An example below has these two elements displayed together. Again, the Watersphere in this design is only showing its core Layer 1, (the Octahedron). The Electrical Structures in both this and the tetrahedron formation, show signs of rotation of the Electrical Structures. Also see Electrical Structure Interactions.
 A confirmation
In the 2002 documentary, Crop Circles - Quest for truth, it was shown that if a perfect triangle was placed over the triangle in the Barbury Castle design, a size difference in the hollow sphere would be the same size as the source of the microwaves.
The lay of the crop is shown below.