Knock-down furniture, known as K-D in the trade, is being reappraised by many shoppers, manufacturers and retailers, in these days of burgeoning shipping charges. Because, of course, knocked-down furniture is designed to be taken home with you in a package, there to be assembled by you.

The actual assemblage of these things is usually geared to people like myself - we own a screwdriver and a hammer but ordinarily don't use them for anything very constructive. In other words, we are definitely not do-it-yourselfers. But assembling K-D is easy even for men. The holes are always pre-drilled and careful instructions come with the package, as well as a picture of the entire piece, totally assembled.

Many of the new pieces don't even require the services of a screwdriver. They are fitted with pegs, just like Shaker furniture, or interlock in a tongue-and-groove construction that means a neat, clean assembly procedure that can be done in a matter of minutes.

The best part of K-D of course, ahd the main reason for its new attractiveness, is its price. Nothing, not even a sofa, costs much over $200, and many items, including upholstered chairs, cost far less. One of the main reasons they cost less is because they come in sections and can be packed flat, lowering primary shipping, distributed, handling and warehousing costs.

Of course, the crucial part is, what do these unassembled marvels do for your room? The answer is that in today's diversified market, you can get almost any look in K-D, from clean contemporary to Early American.

In a living room I designed for a first home in a condominium apartment cluster, I chose a "ready-to-assemble" group in pale pine. I selected two sofa-beds, to make the parlor double as a very much needed guest room. These are clean-lined, and were easy to put together. For the mattresses and pillows, I used foam covered in a natural white canvas, very rugged and handsome with the pale wood of the assembled frames.

A coffee table in the same group makes a convenient night table, as well as a casual place for serving, for books, and for flowers. I covered the two windows on either side of the fireplace with unfinished pine shutters, which give much the same feeling as the furniture.