Every town has got one - a cluster of utilitarian buildings tucked away in one corner. They vary from light industrial units through to massive warehouses and, at the top end, landscaped technology parks full of glossy, glassy offices. The occupying businesses often have weird names and esoteric-sounding functions: 'SST Injection Mouldings', 'KK Exports', or 'Paradigm Solutions'. But what are they exactly? Who works there and what do they do?

They can be disconcerting places to visit out of hours - perhaps you travelled through one on a weekend walk when the units were shut. The car parks will be empty, well, almost empty - there's always one car there. Maybe a security guard, a cleaner, or a lone weekend worker. There's little sign of life otherwise, apart from the occasional group of young skateboarders, who consider this landscape of ramps, pallets and low rails to be an earthly paradise.

Some of the more modern parks have the slightest nod to the plant kingdom which used to occupy the plot - maybe they are landscaped with some low-growing shrubs or a few stick-like trees, but nothing which would support noticeable animal life. In this jungle the trees are steel posts and their lofty occupants are the 'No Parking' and 'Goods Inward' signs. Often a rustic name adorns the site entrance, such as the Old Mill Industrial Estate, perhaps, or the Willows Business Park - sometimes this is taken from a snippet of local history, but more often than not it is a figment of the property developer's imagination, the kind of marketing which gave us in the UK the rash of 1980s 'Barrett-box' housing estates bearing names like 'Badgers Rise' and 'Larkwhistle'.

Keep Out

They don't welcome visitors either. Plates attached to the razor-wire enclosures warn of guard dog patrols, often with a picture of a German shepherd¹, for those who can't grasp this concept in words. Car parks have stripy barriers, and vehicles parked where they shouldn't run the risk of being rounded up by a posse of clampers, or towed away for an extortionate ransom.

For this is the zone of the working man. No poncy architecture here - it's zigzag roofs, asbestos and corrugated steel, chimneys and cowls, and rusting air conditioning units.

And it's impersonal.

Often units have no names at all, only numbers. If you need a particular one you have to find it on the board at the entrance to the estate. This is often poorly positioned; the driver must retain control of his vehicle as he cranes his neck to read a faded signboard displaying maybe 85 units, arranged in a road layout bearing an uncanny resemblance to the Hampton Court Maze. The lettering is invariably one font size too small to be readable, and he has approximately 1.5 seconds to memorise this before the motorists stacking up behind him start to signal their impatience. Fortunately, we rarely need to visit these estates as customers - except for the occasional tile showroom, maybe.

Industrial Revolutionaries

If you work here, you may never meet the workers from the neighbouring unit, or even understand what goes on inside their enclosure. Unmarked trucks arrive with pallets of materials and leave with crates of boxed products, but there's little indication what they are or who they are for. You never see the customers.

The last time you visited a high-street showroom and ordered your new kitchen or UPVC windows, maybe you were charmed by the smart-suited sweet-talking salesman. Maybe you even had a posh cup of coffee while you examined the samples. But it's out here that your order is made up. It's dirty, noisy, and staffed by the kind of men who you might well cross the road to avoid. They're low-paid. They're coarse and tough. They work bloody hard.

Maybe you once saw a warehouse fire door propped open while a boiler-suited worker took a fag break, and inside you spied a teenage mechanic hard at work respraying or refitting a vehicle, to the tinny sounds of BBC Radio 1. So it's a car body shop. Or are they ringing stolen cars? It's none of your business. Maybe they don't look too friendly either way, and you don't really want to find out what those meat hooks in the far corner are for. Pretend you haven't seen them.

Hierarchy

There is a pecking order to industrial real estate. Different classes of park attract different business types and those with slightly more conducive working environments attract higher business rates. In increasing order of desirability we find the following:

Industrial Estates

These attract a mix of business types and a range of unit sizes. You'll find everything from light engineering and manufacturing through to car pounds and larger industrial plants. Often found in towns, by railway sidings and motorway flyovers, facilities can be basic - maybe a burger van provides all the estate's catering needs, but larger factories will have their own canteens. Buildings are often old, sometimes historic, frequently dark and satanic, and usually in a state of ill-repair. Units are crowded together and car parking is limited. Some of the lowest-paid workers are employed here, and public transport links are essential. The working environment is the least attractive, and has the potential to be the most hazardous. When the Buncefield Oil Depot in Hemel Hempstead went up in flames in December 2005, it destroyed many of the units around it.

Retail Parks

A more modern phenomenon, retail parks sprung up in the 1980s in the UK, following the example of the US and parts of continental Europe. Often these are one large warehouse subdivided into varying sizes of units supporting the kind of retail which used to appear on our high streets. Carpets, furniture, electricals, motoring supplies and home improvements are almost exclusively found here nowadays. Supermarkets too, of course, and many of the traditional department stores are also moving in this direction, often to purpose-built shopping villages. Multi-screen cinemas and fast food restaurants are following suit, as their customers abandon the town centres. Convenient it all is, but planet-friendly it isn't; they are always out-of-town and everyone has to combust fossil fuel to get there. Town centres, on the other hand, have suffered greatly, and in some you'll find little more than charity stores and a cluster of new townhouses where the other shops used to be.

Business Parks

Also known as office parks, we start to see vestiges of landscaping at this level - those evergreen shrubs with red berries delineate the plots. Car parking is more generous, as these parks attract office-based businesses. Many were built on the edge of towns in the post-war industrial boom, and some of the 1960s to 1980s architecture - brightly-coloured contrasting window frames, weird geometric brick patterns - is looking decidedly dated. Catering is a problem: if you don't bring a packed lunch, then you may be lucky to have a sandwich delivery service, or failing that, you'll need to walk or drive to a nearby supermarket.

In fact, a whole industry has grown up around servicing these business parks. Look out of the window throughout the day and you'll see an ant-like colony of vans visiting each unit with a wide range of services: caterers, cleaners, landscape gardeners, building maintenance, window cleaners, stationery topper-uppers, even office plant waterers and telephone sanitisers.

Science and Technology Parks

Built to attract businesses and suppliers in a specific industry sector, many of these sprang up in the technology boom of the late 20th Century, and the architect-designed glassy edifices are testament to the free-flowing cash. Large offices, spaced by wide open boulevards and elaborate water features are the norm. Those termed 'science parks' are often related to the pharmaceutical and healthcare industries, whereas 'technology parks' are the realm of information and communication technology firms. A more recent concept is the 'media village', being built to house the decentralising broadcasting industry. These parks are often built on greenfield sites on the edge of expanding towns, and customers are wooed by posh reception areas with uniformed staff to meet and greet. This is important; a company can often be sited close to its competitors.

Headquarters Office Locations

These are the prime sites favoured by the multinational corporations. There are no unit numbers here - the company name and logo will be emblazoned upon a palatial, yet arresting building. These are the contracts for Turner-Prize-aspiring architects to cut their teeth on. Anything goes: neo-Georgian vies with Mayan temple and high-rise space-age glass shards - often in the same building. If you can commission a design the same shape as your product, then all the better. Acres of car parking are a must, often with reserved executive spaces directly outside the entrance, ensuring that the visitor walks past some desirable piece of low-slung gleaming chrome, rather than the maintenance man's Fiat Panda. This isn't the kind of building you'll stumble upon during a weekend walk - you'll see 24-hour uniformed security at the perimeter, as well as plenty of those CCTV cameras which disconcertingly seem to follow your movements.

An Industry Watcher's Guide

We'll end with a few definitions of some of the industrial terms you might see in the names of businesses on your local estate.

• Panel Beaters are skilled car bodywork repairers, specifically following collision damage. They get to use interesting things like planishing hammers and welding torches.

• Injection Moulding is a technique used in making many everyday plastic goods. Molten plastic is injected at high pressure into a mould using a fairly hefty machine, also known as a press.

• Precision Engineers design and manufacture machine tools and other metallic products to a high specification, using computer-controlled machinery.

• Coachbuilders once would have produced those beautiful wooden carriages, but the term has survived for those who construct car bodywork around the chassis.

• Sheet Metal Works manufacture metallic goods using machines to bend, stretch, cut and roll sheets of metal using a range of 'big-boys' toys'.

• Extrusions are products of a uniform cross-section, created by forcing the material through a die. It's the same principle you use in a pasta maker, but industry generally prefers to use metal.

• Hydraulics companies produce, maintain and supply parts for heavy machinery driven by high-pressure fluid supplied through hoses. Excavators and drills are common applications.

There are some common terms which are too generic to be sure what they mean. If you want to set up a company name which doesn't let anyone know what you're actually doing, then choose a few random initials and follow it with any of the following: Systems, Design, Contracts, Services, Imports, Solutions, Products, Manufacturing, Engineering or Fabrications. You'll just have to be particularly nosy if you want to find out what goes on behind that unit's metal shutters.

And Finally

If we've whetted your appetite to discover more about your local industries, then why not risk a short tour? You may be surprised to find what goes on there - maybe your town is the only place in the country which assembles Matchbox cars, or maybe it has the largest banana-ripening warehouse in Europe - who knows? Just beware of the German shepherds.