While I fully understand the different ways that carpets can be made (types of knot, number of wefts, warps on one or two levels, etc) I find it very difficult to observe these characteristics in actual carpets. E.g. I know that with a Persian knotted rug I should be able to see one of the two warp threads between the two strands of a knot, while with a Turkish knotted rug this is not the case. But in practice I can rarely convince myself that I can see this - the ends of the wool are too splayed apart to be able to see where the strands are, even if I bend the rug and look at the base of the pile with a magnifying glass..

Any tips for examining a rug to assess its knot type and other aspects of its structure?