Off the wall or on the floor, it's a knotty problem: With the advantage of expert guidance, John Windsor starts to unravel some of the muddles and mysteries of the Oriental rug market

Five fine silk rugs from Hereke, Turkey, which a Wimbledon accountant bought new for pounds 110,000 from a London dealer two years ago, will not be offered, as he had wished, at Bonhams' sale on 20 January. (The sale is to mark the relaunch of its Oriental carpet department.)

The reason is that Andrew Middleton, Bonhams' recently appointed carpet specialist, warned him the rugs might fetch less than pounds 20,000. The accountant is now wondering how he managed to get burnt.

The rugs, measuring from 2ft x 3ft to 5ft x 7ft, were of exceptional quality - 'I have seldom seen finer,' said Mr Middleton, a former carpet dealer - and of a kind made to order in only a few shops in Istanbul. But they are too new to be collectable, too small and expensive to be value-for-money furnishings, of unfashionably pale colours and of non-symmetrical design. What is more, the same carpets could still be ordered from Istanbul for only about pounds 20,000: the London price was far too high in the first place.

The market for hand-knotted Oriental rugs, as Mr Middleton explained, is not as mysterious as it might appear, especially if you are buying for furnishing. The first lesson is that in each Oriental-carpet sale there are two markets operating side by side: one for collectors and one for furnishers such as first-time home-buyers with limited incomes. Know the difference in taste between the two. Avoid competing with rich collectors. Learn to recognise potential bargains.

Collectors' taste is determined by a simple fact: they tend to buy the carpet first, then curtains and furniture to complement it. Furnishers may already have bargain- basement mahogany and Granny's Edwardian sofa and are looking for a carpet that will not clash.

Collectors go for old carpets (before, say, 1900) and are as likely to put them on the wall as on the floor, especially if they have asymmetrical patterns such as the mehrab (arched prayer niche) on one of those Hereke rugs. Furnishers prefer symmetrical patterns - less 'difficult' to explain to guests and less likely to compete for attention with the host and hostess.

Dark but lively colours tend to blend with furniture better, so furnishers usually shun pale colours. Even collectors are not keen on them. Pale colours are passe, sometimes described as 'Arab taste'. Redolent of sunny climes, they were popular among Britain's Middle Eastern population which swelled after the Shah of Iran was deposed in 1979 and again when Iraq invaded Iran in 1980. In our climate they are something of a mockery.

Unless, that is, you happen to have an airy room with light-coloured furniture and woodwork. Then you could score by snapping up cheaply rugs which no collectors and few furnishers want. For example, Bonhams' sale will have a Kashmir-made Isfahan in an ideal sitting-room size, 12ft x 10ft, with an indigo and mushroom-coloured (symmetrical) medallion on a cream and blue field. Bought new four years ago for pounds 4,000 by a family that has since changed its sitting-room colour scheme, it is estimated at only pounds 800- pounds 1,200.

Beware of garish colours if you want your carpet to hold its value - but they are a good buy if you can live with them and your pockets are not very deep. Besides pink, cream and pale blue, the bright tomato-red of Turkey carpets, an Edwardian delight, is now the pits. (In the late Eighties, East End traders jacked up the price of damaged, poor-quality tomato- coloured Turkeys from pounds 25 to pounds 300. Some young couples still thought they were getting a bargain.) At Bonhams, one 9ft x 42ft, in perfect condition is expected to fetch under pounds 100.

Another rug falling between the collectors' and furnishers' markets is an 8ft x 5ft Istanbul rug of 1900 with two unusually shaped royal- blue medallions on a lemon-coloured ground. Three sides of the border are in stylised Islamic script and one, breaking the symmetry, has a thin, wavy 'cloud band' pattern. 'Difficult. Could be a collectors' thing,' Mr Middleton said. 'It would have been more commercial if it had had a cloud band all the way round.' He has estimated it at pounds 800- pounds 1,200.

Other rugs could be fought over by both collectors and furnishers, such as a pair of 1930 6ft 5in x 4ft 6in Kashan rugs (central Iran), estimate pounds 2,000- pounds 3,000 the pair, made from fine wool. Instead of a central medallion there is an all- over floral design. Its colour, design and condition will attract collectors but furnishers will feel at home with it, too. Mr Middleton said: 'At a glance, you could see it in front of most people's fireplaces. The colours are deep and mellow, so it will go with most things. The design is intricate, very easy on the eye.'

Some rugs look as though they would feel at home only on a collector's wall. One 4ft 6in x 3ft 6in, made around 1900 by the Tekke sub-tribe of the Turkoman in west Turkestan, has an asymmetrical cross-shaped design in brown madder and was intended as a vertically hanging door for Turkoman round tents. It has a small tear and is estimated pounds 400- pounds 600.

Bokhara rugs, with their familiar rows of guls (stylised rose shapes), are as popular as ever with householders. Late 19th-century ones of standard 5ft x 3ft size, a little the worse for wear, can be had for pounds 300- pounds 400 at auction.

Condition and quality are more a matter of taste than you might think. Buyers should not be obsessed with the number of knots to the inch, Mr Middleton advises, nor expect the pile of a century- old rug to be intact, although the wear should be even. Look at the quality of the wool, the liveliness of the colours, the definition of the design. Above all, how does the rug strike you at first glance?

As taste becomes more refined, the desire for symmetry diminishes. Even the rectangular shape of the carpets themselves becomes less obligatory. 'I love to see a bit of irregularity of shape,' said Mr Middleton.

And if you need to have it whispered to you what a Bokhara is, remember: Bokhara, now in Uzbekistan in Central Asia, was the trading point for Turkoman rugs from various tribal regions - Yomut (Turkmenistan) and Belouch (Iranian/Afghan border), Tekke, Ersari and Salor (west Turkestan). Tekke and Yomut are considered to be of the highest quality. Belouch and Afghan come next. Last comes the Pakistan Bokhara, often in non-traditional chocolate, cream or pastel colours and with different wool and knots - still with the guls but out of harmony with the Turkoman tradition. (By the way, heard the one about the social climber who hung a Pakistan Bokhara on the wall?)

Sale: Wednesday 20 January (11am), Bonhams Knightsbridge, Montpelier Street, London SW3 (071-584 9161).

(Photograph omitted)