I have never even heard of CSS border-width property having multiple values, let alone seen it used this way.
ng-grid uses border-width to make arrow icons - like this:
border-width:5px 8.7px 5px 0;
I do not know whether this is ng-grid-specific or whether it is a general property, available in any setting.
Check this plunker out: http://plnkr.co/edit/50vJrs
Never mind all the JavaScript, just play with the CSS, specifically the border-width values in style.css.
Am I out-of-the-loop CSS-wise?