Rambox-CE/ext/packages/ext-theme-neptune/sass/src/grid/column/Column.scss

$grid-header-trigger-border: 
    $grid-column-header-border-width
    $grid-column-header-border-style
    $grid-header-border-color;

.#{$prefix}column-header-trigger {
    background: $grid-header-over-background-color theme-background-image("grid/hd-pop") no-repeat center center;
    border-left: $grid-header-trigger-border;
}

@if $include-rtl {
    .#{$prefix}rtl.#{$prefix}column-header-trigger {
        border-right: $grid-header-trigger-border;
        border-left: 0;
    }
}

.#{$prefix}column-header-last {
    border-right-width: 0;
    .#{$prefix}column-header-over .#{$prefix}column-header-trigger {
        border-right: $grid-header-trigger-border;
    }
}

@if $include-rtl {
    .#{$prefix}rtl.#{$prefix}column-header-last {
        border-left-width: 0;
        .#{$prefix}column-header-over .#{$prefix}column-header-trigger {
            border-left: $grid-header-trigger-border;
        }
    }

}