Text and description quoted verbatim from Microsoft DirectX 7 help file, included here for convenient reference.

The D3DCULL enumerated type defines the supported culling modes used with the D3DRENDERSTATE_CULLMODE render state. These define how back faces are culled when rendering a geometry.

typedef enum _D3DCULL {
D3DCULL_NONE = 1,
D3DCULL_CW = 2,
D3DCULL_CCW = 3,
D3DCULL_FORCE_DWORD = 0x7fffffff,
} D3DCULL;

D3DCULL_NONE
Do not cull back faces.
D3DCULL_CW
Cull back faces with clockwise vertices.
D3DCULL_CCW
Cull back faces with counterclockwise vertices.
D3DCULL_FORCE_DWORD
Forces this enumeration to compile to 32 bits in size. This value is not used.