Laser level saves the day!

Double-wide fabrics are designed to be run sideways for draperies, with the selvedge running at the top and the bottom of the drapery.  This eliminates seams (not that I have anything against seams- sewing seams is how I earn a living!), and with sheer fabrics the absence of seams is a blessing.
This particular pattern is created by heat-setting pleats which, when the fabric is used as intended, run in wavy vertical lines.

But the client wanted to run it the other way, running the wavy pleated lines horizontally.  I suspected this could cause trouble if the heat-set pleats stretched out from the weight of the hem.  And unfortunately, the rep for this fabric company insisted on stating, incorrectly, that the pattern is "woven" and gave the client confidence that she was making a good decision .  I had misgivings about the outcome, but accepted the project.  (Go ahead, say it!  I should trust my instinct!)
To be sure I was cutting on grain, I pulled a thread which provided a cutting guide.  The fact that the grain line didn't follow the pattern proved that the pattern was not woven.  But, anyhow.

Since the fabric was run off the roll instead of railroaded, it had to be seamed to achieve the required width (thus obviating the advantage of the double-wide fabric!).  We French-seamed the cuts by serging them wrong sides together, removing the selvedge in the process:

Then completed the French seam by turning the fabric right sides together, sewing to encase the serged edges.

A small bottom hem was turned and blindhemmed with chain weight inside. 

The tops were pleated with what we call a butterfly pleat: a 4" long pleat, tacked right in the middle.

So, we hung these up in the workroom to see if they would hang straight. 
Well, guess what.  See for yourself:

So this is how we spent a Sunday afternoon.  After letting them hang overnight, we took out the hem and the chain weight.  The hem could barely be pressed because the heat-set pleats would come out.  We didn't see any point in trying to re-table them, since that had already turned out to be unreliable.
So, we set up our laser level on the vertical post of a rolling stand.....

and hung the curtains back up and allowed the laser to indicate a level line.....

 

and I stumbled and crawled around behind the curtain to pin-mark a new hemline as best I could:  And this took a long time, because, naturally, the fabric moved every time I tried to mark it.

 I re-hemmed it, without the chain weight and hung it back up- and ta-da!  It was level! 

We left it hanging overnight again, and it still was hanging level the next morning.  The draperies were installed the following week, and to my utter amazement, they fell exactly where they were supposed to and have held their shape!