WITH SKILL and knowledge you can frame your own pictures. You'll save money and protect your art work from hazards.

Five principal dangers threaten an original work of art.Acid lurks in some cardboards and backings. It can discolor the artwork -- esthetically displeasing, to say the least, and ruinous to its value. Light, especially sunlight, can be filtered with the right glass. Heat, insects, air pollution and moisture, all can be controlled with the proper framing.

There are a number of alternatives to custom framing depending on how much of the process you feel capable of doing yourself. You will get the most help from establishments like Venus Art Frames Plastic Co., 5216 Wilson Blvd., Arlington, and American Art Make-A-Frame with three locations in this area: Leesburg Pike Plaza, Baileys Crossroads, Virginia; in Maryland, Little Falls Mall Shopping Center, Bethesda, and 11770 Parklawn Drive, Rockville.

John Ozolins, a partner at Venus Art Frames, knows his subject inside out, understands the dangers of acidic materials and, in fact, teaches courses on picture care, preservation and framing at the Northern Virgina Community College and the Arlington Public Schools Adult Education Program. The large, pleasant workroom at Venus is fully equipped; you would need no tools of your own.

All kinds of mat boards -- including rag, nonacidic backings, and moldings and glass -- are available. Ozolins and his partner are on hand to give any necessary instruction. Moldings are not cut on the premises and do-it-yourselfers usually don't cut glass, but you can learn to cut mats, dry mount posters and put the whole thing together. The process will take several hours. Ozolins estimates the costs to be: For a 16-by-20-inch project -- including frame, double mat, -- $35 and up. A frame of the same size with an expensive molding can cost $60 to $85. Metal frames cost about 40 percent less.

Manager Nancy Robertson at Art Make-A-Frame, Baileys Crossroads branch, says that about 20 percent of their business is custom framing, the rest do-it-yourself. The staff will help you make an appropriate selection of materials from the many on hand, including a variety of glasses, nonacidic rag board for original works of art, and chipboard and Fome-Cor for backings. rYou can learn to cut mats and how to cover them with fabric if you wish, how to prepare backings and how to put it all together. Glass and moldings are cut by the staff.

Dry mounting is done only on a custom basis. The atmosphere is pleasant and calm. Robertson says that the relaxed environment is deliberate and typical of all three Make-A-Frame shops. Many of her customers find do-it-yourself framing therapeutic; they like the satisfaction of doing a nice, neat job themselves. Some come on their lunch hour to make their selections of materials and return after work to make the frame. On weekdays no appointment isnecessary. Saturdays tend to be crowded.

Robertson estimates a savings of 20 to 60 percent over custom framing. A 14-by-18-inch print or reproduction can be framed -- with a molding at $2.90-a-foot and regular mat board, regualr glass and chipboard backing -- for $24.75; for a fine watercolor of the same size -- using 4-ply rag in front of chipboard for the backing and molding -- at $3.90 per foot, the project would cost $7.85.

Dyer Brothers, 1916 Wilson Blvd., Arlington, doesn't have as much working space as the two establishments described above and offers only metal moldings for do-it-yourselfers plus a few readymade wooden frames. But Tom Holcomb can give you a lot of help, especially in cutting mats and backings. In addition to Nielsen metal sections custom cut in a wide variety of colors, Dyer Brothers carries Nielsen kits, precut from 8 inches ($5.50) to 40 inches ($11.90) in gold or silver color. A 12-by-16-inch precut regular mat cost $1.50; a 30-by-40-inch sheet of 4-ply rag board costs $7.95. Where to Find the Materials

The following firms are some of those in the area who will supply some or all ingredients for framing, if you prefer to work at home with your own tools.

Thomas More Associated, 1790 Lanier Pl. NW, will supply metal sectional chops (a chop is a custom cut piece of molding), considerably cheaper than a kit and not limited to standard sizes.

American Art Make-A-Frame will supply just about any or all ingredients you might need, including wood molding chops and Nielsen metal moldings and kits. Nielsen Metal Moldings can be put together with a screw driver. No extra tools are needed.

At Venus just about any part or all of the materials you need are available.

Hawkeye Art Services, 2305 P St. NW, in addition to fine custom framing, will supply many of the materials you may need: wood or metal chops, precut mats, backings, glass, or the materials to be cut by you.

Kosto's, 3251 M St. NW, no longer has the space for do-it-yourself workshop, but they supply glass, backing and Nielsen kits or custom metal moldings. Ready-to-Hang Frames

Ready-made frames found at stores such as Brentano's Book Stores and Hechinger's are much simpler and really suitable only for reprinted posters, reproductions, documents and some photographs.

Brentano's carries their own one-step frame in silver or gold color and 11 sizes. The smallest, 5-by-7 inches, costs $8.75; 24-by-30 inches cost $32. 1They also have the see-thru frame, a clear plastic box in eight sizes which can stand up or hang vertically or horizontally: 5-by-7 inches costs $4.50; 18-by-24 inches, $33. They also have natural teak frames in eight sizes; 8-by-10 inches cost $15.60; 22-by-28 inches, $40.80.

Hechinger carries the see-thru clear plastic box and an oval shape in two sizes costing $5.95 and $7.95. The box, 16-by-20 inches, cost $14.95. Multimats framed in metal are available from about $6 to $15 depending on size. Metal, wal-mod and bar-mod frames are on hand in seven sizes from 8-by-10 inches at $6.95 to 22-by-28 inches at $19.95. Kits of metal section from 8 to 30 inches are especially reasonable in price. Wooden moldings (chops) to be glued together are also available in kits. A kit of two 8-inch chops cost $1.39; 30 inches cost $3.79. Ready-made wooden frames come in four sizes, $5.75 to $8.95. Step by Step, Page by Page

If you want to do the entire job from beginning to end by yourself, you couldn't have a better guide than the book "Frame It" by Lista Duren, Houghton Mifflin. Every phase of framing is described step by step in clear language. Necessary tools, not as many as you might imagine, are discussed.