A little time devoted to giving wobbly chairs, tables and other "sick" furniture simple first aid can often restore their use and looks.

In instances where the problem is structural-where legs or rungs have loosened or drawers have started to come apart-the quicker the repairs are made, the simpler they are likely to be and the greater the chance of saving the piece.

Many tables and some chairs have legs held in place with bolts or screws that pull them tight against the ends of the side rails or "aprons" by means of angled metal braces. When one of the legs starts to wobble, chances are you only need to tighten the wing nut or bolt that goes into the leg to pull it tightly into position once more. If this kind of problem is ignored too long the amount of wobble will get worse, and the leg eventually will splinter, crack or fall off.

If the leg that is loose has no such metal brace, or if tightening the nut that holds this brace in place doesn't correct the looseness, your best bet is to add a block of wood. It should be at least 1 1/4 inches thick and should be screwed to each of the side rails, after drilling pilot holes first to prevent cracking. A hole bored through the center of this brace will allow insertion of a long, heavy screw so that it goes into the corner of the leg to brace it firmly. Applying glue to the ends of the rails where they butt against the top of the leg will help strengthen the joint.

In many chairs and small tables there are no side rails or aprons going around under the rim; instead the ends of the legs fit into holes bored into the bottom of the seat or table top. Where these glued joints loosen, re-gluing is required, but this calls for more than just squirting a little extra glue into or around the joint. The best way to re-glue an old joint is to take it completely apart, scrape off the old glue, then apply new glue and reassemble. Clamps should be used to apply pressure until the glue hardens.

In many cases the joint loosens because the wood legs or rung has shrunk, or because the hole is slightly enlarged. Most glues do not bond well when there is a loose fit, or when there are cavities in the joint, so before re-gluing make sure parts fit snugly Sometimes the end of a rung or leg can be enlarged by wrapping it with one or two layers of linen or cotton thread. In other cases it may be easier to force thin splints of wood (tooth-picks work well) around the loose part.

If there is only one leg or one rung loose, taking the entire chair apart is impractical. Use a pointed instrument to scrape out as much of the old glue as possible. Squirt frest glue into the joint with a hypodermic-type glue injector or squeeze-bottle with a narrow nozzle, then force pieces of thin wood into the joint, and trim off any excess after the glue hardens.

Hardware stores sell special types of wood adhesive for loose furniture joints. They come with special applicator tips for squirting into narrow crevices around loose-fitting pieces and are designed to help swell the end of the rung or leg so that a tighter fit is possible.

When drawers in chests or cabinets start to grab or bind every time they are pulled open, the first thing to do is take the drawer out completely and inspect all joints to see if any are loose or starting to come apart. Here again, the solution is to re-glue any loose joints.

If they cannot be taken completely apart, pry them open as much as possible and use the tip of a knife to scrape out most of the old glue. Then apply fresh glue and clamp. For those who do not have the long clamps needed for jobs of this kind, a simple solution is to wrap the drawer with a rope tourniquet. Use pads of cardboard to protect the corners and edges, and apply only enough pressure (by twisting the stick) to ensure firm contact-not so much that all the glue is squeezed out of the joint.

When a leg, rung or back splits, an effective repair can almost always be made by working white stain-proof glue into the joint, then clamping the split with clamps or by wrapping tightly with string until the glue sets. If the piece must withstand sideways stress, it can be reinforced by drilling a hole through this hole. The ends of the dowel can be camouflaged by touch-up with stain to match the finish.

To fill scratches, gouges and nicks on wood furniture, use one of the various putty sticks or touch-up pencils sold in lumber yards and hardware stores for filling nail holes in finished paneling.

Directions for filling nail holes say to rub these sticks back and forth over the hole as you would a crayon-the soft compound fills the hole. A better method is to heat the blade of a knife first, then use the warm blade to "butter" the material over the depression. Build it up to a little higher than the surrounding surface, then use a piece of stiff plastic (a credit card is great for this) edgewise to scape the excess off. This patch will be duller than the surrounding area, but the gloss can be restored in most cases by applying wax.

Burn marks-the kind often caused by careless smokers-can usually be camouflaged, or even entirely removed, by first scraping carefully with the point of a knife blade held with its cutting edge at right angles to the surface. Scrape back and forth until all the scorched material is removed, then touch up the light area that remains with a little oil stain. CAPTION: Illustration 1, Splints can be used to tighten wobbly rungs or legs on some chairs.; Illustration 2, Tourniquets can help regluing of loose drawers, cabinets or tables tops.