layout/Separation Separation, e.g. of a layout cell from its neighbor, via a vertical gutter of defined width, with or without a vertical line in its middle. No gutter at all (0px), and without a vertical line, of course. A small (17px) vertical gutter without a vertical line. A small (17px) vertical gutter with a vertical line in its middle. A medium (31px) vertical gutter without a vertical line. A medium (31px) vertical gutter with a vertical line in its middle. A large (63px) vertical gutter without a vertical line. A large (63px) vertical gutter with a vertical line in its middle.