First of all, stay away from machine-made rugs, popularly known as "Carmel rugs," named after the bankrupt company once owned by the late Rabbi Avraham Shapira. The best way to differentiate between a machine-made rug and an authentic handmade one is to turn it over: On the reverse of a machine-made rug, one can see the white netting on which the woolen threads were knotted (that's in the best case; sometimes the fiber is synthetic), and the pattern can barely be seen through this netting, which also makes the rug very stiff.

The opposite is true of an authentic rug: the higher the quality, that is, the denser and more delicate the rug, the softer it is. Most importantly, the two sides look very similar, and in any case, it is easy to see the entire pattern even on the reverse side. Truth be told: A rug whose knots are not hand-tied has no value, even if it's true that it is usually children who sit in front of the loom and strain their eyes knotting the rug, on which we later walk, scatter cigarette ashes, or spill coffee.

It's also time to stop using the annoying generic name "Persian rug," a heritage of Eastern Europe, which is used by many to describe carpets whether they come from Turkey, Afghanistan, Bukhara or India. An authentic Persian rug is in fact the crown jewel of rugs (of course not always, because there, too, they make poor or commercial quality rugs) but who can afford to buy one?

To check out a fine Persian carpet, one must - once again - turn it over. An expert will run a fingernail over it, and the rule is that the sound of the fingernail scratching the rug should be as clear as the sound of china: that is the sign that the knots of the rug are of sufficient density, and that the wool is strong and not coarse.

Those who are less expert are invited to use a magnifying glass, which every self-respecting rug merchant keeps on the counter. In fine rugs, the number of knots per square centimeter can reach 100 or more, and this allows us to calculate the amount of work and the time invested in making it. And we still have not discussed the various patterns, and the names.

At this point it is important to know that there is one major difference between a Persian rug and any other Oriental rug - whether Turkish, Afghan or Bukharan: In a Persian rug, every knot (which looks on the reverse side of the rug like an embroidery stitch) stands by itself on the warp thread, whereas in other Oriental rugs two warp threads are stitched into one knot. This would seem to be a minor difference, but it doubles, or even triples, the amount of work invested in a Persian rug as compared to the work required to make its close relatives.

There is nothing more important than going to the markets, looking at and feeling as many rugs as possible, in order to learn about these minor-major differences. Sometimes I watch from the sidelines, with pity, customers at mall-stores (like Beitili) who are tempted into buying the rugs sold by the chain; the names are in fact correct, and the rugs even have "certificates" of authenticity (these are mainly Afghan or Baluch rugs). Sometimes the patterns are even traditional.

The only problem is the absence of knot density, which proves that although the rugs were in fact handmade, the work was done quickly, on a commercial assembly line. So it's better not to rush: For almost the same price, one can sometimes buy a similar rug in the flea market in Jaffa, with double the density.

The problem is that in the markets, whether in Jaffa or the covered market of Istanbul, the merchants tempt you with smooth talk, spread beautiful carpets before you, invite you for tea: The rule is to separate the deal itself from the games surrounding it, and not to feel obligated, because of a cup of tea, to buy a rug that you don't really want. Here are a few universal rules:

* Don't be tempted into buying the first rugs the merchant shows you. These are usually (you can assume that he has already realized that you are not a big expert on the subject) the poor quality rugs that he has not been able to get rid of for years. These will almost always be shiny-silky rugs, of the type that make an impression on the uninitiated. Such shiny, imitation silk rugs are usually made of wool or of cotton and wool, which have undergone a chemical process to make them shiny. After a short time in your house, the shiny, fur-like covering will fade and wilt, and it will look like trampled grass.

* Don't be tempted to buy a rug that the merchant calls antique, only because it's all faded and patched. Not every old rug is good, and it's better to buy one that is new or relatively so, that will serve you for many more years.

* Another trap into which many fall for lack of experience, is the thickness of the rug, and the pleasant feeling of walking on thick fur, which the uninitiated tend to find a positive feature. That is not the case: Thick rugs are rugs that have something to hide beneath their inviting fur. Usually the paucity of knots, which can be discovered when the rug is turned over.

Everything we have said until now concerns knotted rugs. Another world, with different rules, is that of woven rugs, also known by their Turkish name, kilim. These can be divided into various types, which combine techniques of weaving and embroidery, or weaving, embroidery and knotting, in the same rug.

These rugs, which are made with a mixed technique, are called soumak by the merchants, and they are very common in Israel, and not so expensive. Here, too, one should pay attention first and foremost to the density of the weave. The Land of Israel and its surroundings have made a significant contribution in the field of weaving, and the local style - that of Sinai, the Negev and Jordan - has an international reputation. Therefore, instead of rushing to the markets of Istanbul and buying a kilim of doubtful value, one can go down to the Bedouin market in Be'er Sheva or to the Christians' Street in the Old City of Jerusalem, and find treasures of local manufacture: These are long, narrow carpets woven by women on an improvised loom, held down to the ground with stones, and then sewn together according to the desired width. These rugs have a great deal of charm, and they are already of a disappearing species, but still not so expensive.

In the Bedouin community of Lakia in the Negev, the women of the village, under the leadership of an Englishwoman who converted to Islam and married one of the locals, have set up an association of weavers of traditional-style rugs, and their handiwork can be seen and bought by making an appointment over the phone.

The following are a few more characteristics of knotted rugs. Foremost in the groups of classic large rugs are Anatolian rugs: The most outstanding among them are made in the pattern of the mihrad, or prayer niche, of the mosque, with a mosque lamp trailing from the edge; many other rugs, which are equally as good, are in repeated geometric patterns.

The second group, Bukharan rugs, is easy to identify: These rugs come in a few shades of red, black and white, and in a small number of patterns that represent stylized lilies or spider patterns. The Bukharan rug has become an aristocrat in the hierarchy of rugs, thanks to the strong, long-lasting wool of the sheep of Central Asia - after all, the rugs there are meant first and foremost for insulation from the cold in the yurta, or the nomads' tent.

The knotted rugs most easily available in Israel are those called Afghan or Baluch rugs. These include many, as mentioned, that are manufactured commercially, but with a little patience one can find better ones, too. The classic pattern of an Afghan rug - many Afghan rugs are made in "Persian style" or "Bukharan style" - depicts a stylized tree of life, whose branches spread out to the sides like a type of fir tree, which is completely surrounded by a framework of geometric patterns. Afghan rugs can be very simple, with one geometric pattern that is repeated again and again, with a surrounding framework in another pattern.

It is better to let real connoisseurs deal with authentic Persian rugs. First one should dream about them, read about them in books, study them, look at their classical pattern in museums. It is not a subject that can be taught overnight.

How does one conduct negotiations when buying a rug? There are many methods. The best is to name a price (the price must be reasonable, of course, not too low and not too high), and not to budge from it. If the seller does not agree to sell, leave the shop: If he runs after you, it means that you've made a good deal. If not, you can always go back and offer a little more.