"WHATEVER YOU learn here will not turn a $200 rug into a $2,000 one," rug restorer Melissa Wood warned in her recent two-day rug repair workshop at the Textile Museum.

"But I hope you will learn not to be afraid of your rugs. Remember: Whatever you do to a rug, you can undo," she said.

Overcasting, patching, reweaving, rebuilding the rug foundation as well as tying Ghiordes and Senneh knots were just some of the repairs discussed in the weekend workshop.

"However, before doing any antique rug repairs," cautioned Wood, "be certain you want your rug repaired. Repairs can affect a rug's antique value. What I will show you in this workshop is primarily for conservation purposes."

She provided each student -- all of whom were either carpet dealers, repairers or collectors -- with a patch of carpet, a canvas, needle, thread, yarn and what appeared to be a small rolling pin.

Wood recommended a long table -- "as long as your rug, if possible" -- when making rug repairs. "If you don't own a long table, a board that can be nailed into will do," said Wood. One student suggested a door with all the hardware removed; another said a needlework canvas frame -- properly braced -- will work.

The first repair Wood demonstrated was overcasting. "Overcasting," she explained, "is the stitch to use to prevent the carpet knots from falling off. I advise doing it first on patches like the ones you have and then on utilitarian rugs until you become proficient enough to do it on more expensive ones."

The overcasting stitch secures the knots located on the carpet's ends. Work from the backside of the rug and use a natural fiber thread -- as opposed to polyester or nylon, which can cut through the rug fibers, warned Wood. "Pass the needle in the same direction as the warp thread [vertically]. Catch a few weft [horizontal] threads, go into the rug, coming out at the fringe. Circle the fringe with your thread and go back down into the rug.

"It's a good idea to vary the depth of this stitch in order to distribute the tension evenly -- not all on one row of knots," said Wood. "And be prepared to redo the overcasting -- it wears out every 7 to 10 years, depending on how much traffic your carpet receives.

"Putting a new edge or binding on your rug is one of the easiest repairs to make. It can make a carpet look better right away and takes no time. You can also mend parts of the binding if only sections are worn out. Tack your rug edge onto your wood working board. Stretch a plain cotton or wool cord -- depending on what fiber your rug is made of -- along the edge of the rug.

"Tie the cord at each end to a nail -- without this tension, the side of the rug will ripple when the new binding is finished. Sew the cord into the corners of the rug. Then, using three-ply thread -- available at the Textile Museum and yarn shops -- sew in a wrapping-type stitch around the cord, securing it to the carpet after each wrap. Any number of additional cords may be added, but remember to secure each onto the wooden surface to maintain proper tension." And when replacing an entire binding, choose a color from the rug but one shade duller. Otherwise, the binding will take the limelight away from the rug itself.

Sometimes the carpet's interior knots come loose, as does the rug's canvas foundation. When both have occurred, Wood prefers to repair the foundation first.

"Square off the jagged canvas -- this makes the reweaving easier -- but be careful to cut before or after the knots and not through them," Wood said.

"Slip your rolling pin under the damaged section -- back side up. Tack it down. Using wool or cotton thread -- again, the fiber used in the rug -- reweave the warp threads first -- going from top to bottom. Then reweave the weft threads -- going across. Do not knot the weft threads. Do one back-and-forth stitch, cut the threads and leave them loose.

"For coarse rugs you will need a thick warp thread, which is not easy to find. An alternative is to ply your own warp thread for added thickness." Wood then showed how to thicken the thread. She took the ends of a thread in either hand, untwisted them and then let go. The two threads coiled together to become one. To secure the coiled threads, Wood passed it once through beeswax.

Next, Wood demonstrated two ways to repair the pile -- patching the rug or reweaving. She uses patches left over from unrepairable rugs.

"Patching has one main advantage over reweaving," said Wood. "Even if you're not using a patch from the same rug, the old patch dyes will remain the color they are. No matter how well you match a yarn for reweaving, it will undergo a color change as it ages. New dyes don't remain the same one year after they're bought. Because the dyes change at different rates, it can be very hard to match yarns."

Sometimes, she said, you have to reduce the rug to make a patch. She also recommended step-cutting. The rug patch is cut in steps so that the seam is not in a straight line. "Step-cutting takes more time, but looks very professional," noted Wood.

To put in a patch, Wood uses a blind stitch.

To reweave, Wood first demonstrated the knot most commonly used. The Ghiordes or Turkish knot (used in 99 percent of Oriental rugs) is made by wrapping a three-ply yarn around two warp threads, crossing the yarn ends and then pulling the yarn down to form a knot. Wood prefers to use old wool if possible -- again, to avoid dye discoloration and also because old wool is less slippery than new. (New wool can be given the texture of old wool by running it through beeswax.)

"Always reweave from the bottom up," stressed Wood. "Otherwise the wool will hang in your way.

"Cut the yarn threads after completing each knot, until you become competent; then you can move along without cutting," suggested Wood.

Wood also demonstrated the Senneh or Persian knot, which is used for finer designs. The yarn encircles only one warp thread at a time and winds loosely around the other.

To make this knot, the yarn crosses behind the left warp thread to the front, then wraps around the right warp thread, coming down through the center. The yarn thread is left hanging -- the density of the rug is what makes this knot secure; the warp threads are almost on top of each other. Because the yarn knots after each warp thread (instead of after two, as in the Ghiordes), reweaving Senneh knots is a long and painstaking process that Wood said is best left to the experts.

Twice as much wool is needed in making Senneh knots as in Ghiordes knots. When reweaving Senneh knots in a finely woven kilim, Wood prefers to use cotton, since wool is too thick and tends to untwist.

Finally, the last and most enjoyable step is trimming the yarn to see what you've done. Any repairs you make will stick up above the original pile. "It's important," said Wood, "to be as alert at this stage as you were while reweaving. If you're tired, put the rug down and trim it later. I've seen some beautiful reweaving jobs ruined by a sloppy trim." Wood uses a nail scissors for trimming, but said any curved blade will do. "Press on the blades as you trim," said Wood, "and trim in the direction of the pile."

To be sure the knots don't fall out, Wood advised tapping the face of the rug with a flat rubber hammer in the same direction as you were weaving. Then place a white Turkish towel over the pile and press a steam iron in the direction you want the pile to lie. Also press the rug's backside. Wood then sometimes applies wax to the just-pressed back.

A quick repair you can make if the pile has worn thin in small areas is to paint the foundation of your rug. This is recommended only for very small sections. "Never," said Wood, "Paint the wool part of your rug, only the foundation." Textile watercolor dyes -- 15 colors for $30 -- are available at the Textile Museum shop. "Remember to tell your carpet cleaner if you've made any paint touch-ups; the colors could run."