mail/src/sass/_grid.scss

// Make a Grid
// Use makeRow and makeColumn to assign semantic layouts grid system behavior
@mixin makeRow($gutter-width: $grid-gutter-width) {
    margin-left: $gutter-width * -1;
    @include clearfix;
}
@mixin makeColumn($columns: 1, $offset: 0, $column-width: $grid-column-width, $gutter-width: $grid-gutter-width) {
    float: left;
    margin-left: ($column-width * $offset) + ($gutter-width * ($offset - 1)) + ($gutter-width * 2);
    width: ($column-width * $columns) + ($gutter-width * ($columns - 1));
}
@mixin pushColumn($offset: 0, $column-width: $grid-column-width, $gutter-width: $grid-gutter-width) {
    position: relative;
    left: $offset * ($column-width + $gutter-width);
}