I think that when you lay out the fabric lengthwise the stripes are going to run accross the fabric. In other words, the length of the curtains is the length of the fabric and the width of the fabric will be the width of the curtain panel. the chevron stripes will run horizontal to the floor then. In other words you will not have to piece the length. Vertical and horizontal are always hard to remember. keep in mind that horizontal/horizon. Vertical is up and down. so I think that when it says the chevron runs vertical to the selvedges, I think they are saying they cross them. If they ran horizontal to the selvedges the chevron strips would run the same direction as the selvedges. May I say, they need to hire a better writer for their descriptions! :0