Counting symmetrical knots

In order to count the number of knots, I'm going to turn the carpet over and work from the back. In order to assess the fineness of a carpet, we need to find out how many knots there are in a square inch. So I'm working from the back - this is the back of the carpet. It's much easier to see the individual knots because there is no pile in the way. So I'm going to work in this area here. What I'm going to do first is count the number of knots that are horizontal ... so across the carpet. Each knot is tied around two warp threads so it forms two little bumps on the back of a carpet. So I'm going to count how many bumps there are ... one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve - so there are twelve bumps in that one inch. If each knot forms two bumps, I simply divide twelve by two and I can say there are six knots in an inch across the carpet. I then do the same, finding out how many knots there are vertically. There's one, two, three, four, five, six - So there are six knots horizontally, six knots, vertically, multiply the two of them together - 36 knots per square inch in this carpet, which is a fairly coarse carpet.