Many examples of ethnographic art have designs which can be viewed as taking two copies of a strip pattern and sewing them together along one edge of the strips. In many cases, the resultant designs have symmetry that is not appropriately modeled by either traditional strip patterns or by wallpaper patterns. For example, while most of these double strip patterns can be extended to wallpaper patterns, that extension is not always unique and, we argue, is not necessarily a good representation of the artistic intent of the person who created the design. We classify the possible (one-color) double strip patterns and show artifact examples of many of them. In particular, we focus on a large number of such designs from pre-colonial Peru and from Papua New Guinea, demonstrate the substantial differences between which classes of double strip patterns these two regions use, and offer some suggestions as to the reasons behind these differences.