They're just pads of lined paper that are used in the legal profession for for taking notes. Insetad of a standard 8.5 x 11" page size, they are typically 8.5 x 14" -- which has come to be known as "legal size," at least here in the U.S.A. Nothing more to them than that; any pad of lined paper would do just as well (although I suppose it wouldn't be "authentic," so purists might object).