Edit in JSFiddle

<div class="uk-container">
    <div class="uk-grid">
        <div class="uk-width-1-3">
            <div class="uk-panel uk-panel-box">Left Side</div>
        </div>
        <div class="uk-width-1-3">
            <div class="uk-panel uk-panel-box uk-panel-box-primary">Center</div>
        </div>
        <div class="uk-width-1-3">
            <div class="uk-panel uk-panel-box">Right Side</div>
        </div>
    </div>
</div>
<div class="uk-container">
    <div class="uk-grid">
        <div class="uk-width-1-1">
            <div class="uk-panel uk-panel-box">Added panels to highlight the grid sections.</div>
        </div>
    </div>
</div>
body {
    margin: 20px;
}
/**
 * Manually add a margin
 **/
.uk-container {
    margin-bottom: 20px;
}