How to create corner borders with a single border artwork

I create a little script years ago to create a mitered one inch selection on the document left side. I used the script in action that fill it with a frame pattern in a new layer. the was the duplicated an rotated 180 and aligned to the document right side. These frame layer were above the top and bottom frame pieces. In case there were rounding issues with the mitered selection there would be no gaps in the corners for the top and bottom frame pieces were not mitered. 

// The author accepts no liability for any problems arising from its use.


/*
<javascriptresource>
<about>$$$/JavaScripts/OneInchMiteredLeftEdgeSelection/About=JJMack's One Inch Mitered Left Edge Selection.^r^rCopyright 2009 Mouseprints.^r^rScript utility for action.^rNOTE:One Inch Mitered Left Edge Selection!</about>
<category>JJMack's Action Utility</category>
</javascriptresource>
*/

leftsideframeselect(); 

function leftsideframeselect () { 

// validate that a document is open 
if (documents.length < 1) { 
	alert("No Open Document!"); 
	return; 
	} 

// Set the ruler units to PIXELS
var orig_ruler_units = app.preferences.rulerUnits;
app.preferences.rulerUnits = Units.PIXELS;

var doc = activeDocument;
var height = doc.height.value;
var dpi = doc.resolution;

var frameRef = [
[0,0],
[0,height],
[dpi,(height-dpi)],
[dpi,dpi],
]

doc.selection.select(frameRef);

// Reset units to original settings
app.preferences.rulerUnits = orig_ruler_units;
}