What term describes when the threads of one layer of fabric lie in the valleys of the opposing layer of fabric?

The term that accurately describes when the threads of one layer of fabric lie in the valleys of the opposing layer of fabric is "nesting." In the context of fabric layers, nesting refers to the way the threads interweave or position themselves in a complementary manner, allowing for a better fit and enhanced structural integrity. This technique can be crucial in various applications, including aerospace components, where the alignment of fabric layers influences strength, weight, and overall performance.

The other terms do not convey the specific arrangement of threads that nesting describes. For example, laying typically refers to placing fabric in a flat position without implying any specific arrangement with respect to other layers. Stacking generally refers to layering items one on top of another without regard to the interlocking of the threads. Overlaying simply means placing one layer over another without the intimate interaction described by nesting. Thus, nesting is the most precise term for this particular scenario where threads interlock in a beneficial fashion.