What is Double 6 called?

What is Double 6 called? A double six is a set of 12 lines in the 3-dimensional projective space, often written, the notation being due to Schläfli, as a matrix: and having the property that two lines among those 12 are secant if and only if they are not placed on the same line or column of the matrix.

A double six is a set of 12 lines in the 3-dimensional projective space, often written, the notation being due to Schläfli, as a matrix: and having the property that two lines among those 12 are secant if and only if they are not placed on the same line or column of the matrix.