They call themselves ski salespeople and tech reps. They allow prospective buyers to ski on expensive skis before parting with $200 or $300.

But they stack the deck. They tune the skis so highly -- filing the edges, filling the gouges, waxing the bottoms -- that the skis can't ski badly even if you do. They are very careful about assigning their skis, trying to suit skier to ski so exactly that the fit is as near perfect as possible.

Bill Nicoll, one of the ski reps working in the mid-Atlantic area, has 45 pairs of Rossignol skis in his Rossignol van, and he travels his territory tirelessly, hitting as many ski areas as he can in the too-short season.

When he gets to a ski area, he sets up his truck near the slopes and waits for customers. They aren't shy. "I'm there to sell skis," Nicoll said. "More than half of the people who try the skis are just curious, but the rest really want to buy."

Nicoll doesn't sell the skis he carries, he just gets the skier interested, and resort ski shops as well as the hometown shops reap the profits.

Nicoll's technique is good. He talks with the skier to determine ability, style and preference. Then he recommends a ski.

"Try this one," he'll say. "It is good in quick turns, sharp turns. You can make long carved turns, but you'll find it responds better when you skid your turns."

And you go out and try it, and darned if he isn't right.

"A lot of people want to try a racing ski, a ski they have to work all the time, when really they could have more fun on something a little less demanding," Nicoll said. "People say they want the top of the line, but I'd rather put them on a recreational ski."

Nicoll often recommends a slightly longer ski than many skiers use. "I feel people are ready for a longer ski," he said. "The shorter length is a det riment to better skiing." Nicoll said that the prejudice against longer skis comes from the time when longer ones were stiff, and therefore harder to use. Today, he explained, new construction methods make it possible to have a softer, more responsive ski in a longer length.

Like the other tech reps who tour the ski areas, Nicoll does not charge skiers who use his skis. He requires only two forms of positive identification, a major credit card or a season pass for the ski area before he will lend skis for an hour and a half or so. He figures a skier needs four or five runs to get the feel of the skis, but he also needs to lend the same pair to three or four people a day.

Ski shops, on the other hand, charge for using their demo skis. But they sweeten the pjot a little by letting you apply the rental charge to any skis you buy at the shop.

While a demo rental from a slopeside ski shop usually is preferable (most slopeside shops allow you to try more than one pair in a single day for the same rental price), if you're going to buy the skis you might prefer getting the demo from your usual shop.

On the other hand, your shop may not have the skis you are interested in, in your length, in the demo racks. You may need to shop around to find the ski you want to try.

Ski shops get a special rate on demonstration skis because manufacturers are convinced that once you try their skis, you'll buy them. Most demo skis are handpicked and checked more thoroughly for compatibility and for such problems as warping than other skis. These are, after all, the showoff skis. As a result, you will ski the model at its best in a demo program.

If you are interested in trying a pair of demos, you can ask your local ski shop if it has a program. One-day rentals range from $10 to $20 for these high-price, high- and mid-performance skis. Of course, you'll have to have your own boots (rental boots, most of which have Spademan bindings, are not compatible with the step-in bindings on demo skis). You also must guarantee the safe return of the skis. Some shops have insurance you can buy.

Alternatively, you can call your ski shop and ask for the schedule of the tech rep from the company that makes skis you are interested in. Kastle, K-2, Kneissl, Fischer, Alan and Rossignol have demo vans. Tech reps don't publicize their itineraries as much as you might wish; often the only way you will find a demo truck is to happen upon one.