Thanks so much for this article. This type of lapped seam was new to me, so I did a little research online. I have seen it labeled as "turned lapped seam" and "double lapped seam". Apparently it is a very strong seam, and is often used for motorcycle attire, tents and military usage. I appears to be easier to be accurate than the usual lapped seam, so I intend to try it out soon.