src/themes/website/styles/resizables.scss

.resize-handle {
    background: transparent;
    position: absolute;
    z-index: $z-index-base + 1;

    &.resize-handle-right {
        cursor: e-resize;
        width: 5px;
        right: 0;
        top: 0;
        bottom: 0;
    }

    &.resize-handle-left {
        cursor: w-resize;
        width: 5px;
        left: 0;
        top: 0;
        bottom: 0;
    }

    &.resize-handle-top {
        cursor: n-resize;
        height: 5px;
        left: 0;
        right: 0;
        top: 0;
    }

    &.resize-handle-bottom {
        cursor: s-resize;
        height: 5px;
        left: 0;
        right: 0;
        bottom: 0;
    }
}