Sheets of rigid clear plastic, available in hardware and department stores as well as in home centers, hobby shops and plastic specialty stores, have many uses around the home -- some practical and some purely decorative.

The plastic can be easily cut, drilled and sanded with ordinary hand or power tools, and used to make ornamental shelves, bookends, magazine racks, display cases, picture mounts, terrariums, decorative racks for glasses and bottles, and even small pieces of furniture.

The most widespread use for these clear plastic sheets is as glazing material to be used instead of glass where safety and resistance to breakage are of paramount importance: in hazardous locations such as shower doors and tub enclosures, ground-level windows in basements and ranch homes, storm doors, garage doors, and similar places.

Using shatterproof clear plastic instead of regular glass in such locations could minimize the danger of breakage and almost completely eliminate the danger of serious injury in the unlikely event that the plastic breaks.

Many states and local building codes now require an approved type of safety glazing material instead of ordinary window glass in hazardous locations such as those mentioned. Products approved by the American National Standards Institute include tempered, laminated and wire glass as well as several kinds of elear plastic. Plastics are much easier for amateurs to work with and install, and usually cost less.

The two most widely used clear plastics are acrylics and polycarbonates (vinyl and polystyrene are also available clear, but not all are suitable for outdoor use and most are not approved by the Safety Glazing Certification Council). The acrylics and polycarbonates are suitable for outdoor and indoor use, and both are almost as clear as glass, but polycarbonate is much more expensive. (Lexan, made by General Electric, is probably the best known brand.)

Lexan costs considerably more than Plexiglas or Lucite, the two most popular brands, but it is also much more resistant to breakage where heavy blows are likely to be encountered or where maximum resistance to breakage is required.

Plexiglas (Rohm and Haas) and Lucite (DuPont) come in a variety of sizes and in thicknesses from one-tenth to one-quarter of an inch. The thicker the sheet, the stronger and more resistant it is to breakage. Acrylic sheets also come in various translucent or opaque colors for use where a decorative effect rather than transparency is required, but the colored sheets are not as readily available as the clear.

Most acrylic plastic sheets come with a protective paper facing on both sides to prevent scratching, so when possible leave this covering on both sides while cutting, drilling, or installing. For cutting with hand saws, use either a hacksaw or a wood-cutting saw with fine teeth; with power saws use a blade with fine teeth or a blade suitable for cutting plywood, thin veneer, and plastic laminate.

As easy, quick way to make straight cuts is the scribe-and-break method. You will need a plastic cutting tool (sold by plastic dealers) and a straightedge. Place the straightedge alone the line to be cut, then score deeply with several strokes of the cutting tool blade, as illustrated -- five to six strokes for thicknesses up to 3/16ths of an inch, and about 10 strokes for onequarter-inch thickness.

Place the scored sheet over a dowel about three-quarters of an inch in diameter so that the score mark is directly over the dowel, and press down hard on both sides with your hands. The sheet will snap neatly along the line just scored.

When cutting sheets for use in storm doors or windows, remember that this material expands and contracts more than glass, so cut the sheets slightly smaller to allow for this. Generally, about 1/16ths of an inch less along each side will be adequate if the opening is up to 36 inches in width or length, and about one-eighth of an inch less if it is much more than this in one dimension.

For storm door inserts the thinner material -- about 1/10th of an inch think -- will be adequate, and this will usually fit right into the same frame as the original glass. Thicker material -- 3/16ths of an inch -- is often preferable in regular windows at ground level or for garage doors where there is more likelihood of damage. Ordinary glazing compound can be used, but for maximum strength and watertightness, silicone rubber caulking material will work best and last longest.

After pieces have been cut to size and shape, regardless of whether by saw or hand-scribing, smooth off the edges and any sharp corners, even if these edges will be covered by molding. This increases resistance to breakage and, in the case of those assemblies where edges will show, greatly enhances the appearance of the finished project.

Use a medium grit (No. 80) aluminum oxide sandpaper