"When you're makin' things handmade, you can't make two pieces exactly alike to save your life," says Chester Cornett, the subject of "Hand Carved," a fascinating new documentary portrait from the estimable Appalshop film group in Whitesburg, Ky. Cornett, a solitary craftsman who specializes in handmade rocking chairs, was persuaded to let a crew directed by Herb E. Smith record his labors and commentary in the fall of 1977 while makng one of his specialties, a tall, eight-legged, "two-in-one" rocker.

Shown today and tomorrow at the K-B Janus as part of a series of Appalshop productions, the feature-length "Hand Carved" seems to have been undertaken in the nick of time. Ailing and aging, Cornett was able to complete only one more commission before entering a Veteran's Administration hospital in Cincinnati. It's been three years since he's taken ax and chisel to sassafras wood in the manner documented with such tender attention by Smith and his associates.

Cornett, wild-bearded, wild-maned and more than a little wild-eyed, sustains a running commentary of technical pointers, recollections and homely philosophy from the act of felling a suitable tree on family acreage in southeastern Kentucky to transforming that timber into a capacious Cornett original in his small Cincinnati workshop. "I don't like to kill a tree," he confides, "but God made those trees to grow for man's purposes . . . My favorite workin's wood is sassafras. It bends good without breakin' and it smells good. I like to smell the wood while I'm workin' it."

Most of the Appalshop documentaries have been motivated by the desire to celebrate regional crafts and folkways, and they've often succeeded beautifully. The finest in the current series are "Nature's Way," the short that shares the program with "Hand Carved" at 3:30 and 7:30, and "Waterground" and "Quilting Women," half the program of four shorts scheduled for showings at 1:30, 5:30 and 9:30 p.m. both days. However, before the encounter with Cornett, the Appalshop filmmakers had ventured beyond 40 minutes only when putting together a feature-length compilation of highlights.

Inaugurated in 1969 as part of an OEO program to establish regional filmmaking centers for unemployed young people in a number of poverty-stricken locales, the Appalshop proved the happy exception to an otherwise ill-fated program. As a rule, the centers folded because the intended beneficiaries lost interest or absconded with the equipment. In Whitesburg, the kids ended up using and mastering the facilities placed at their disposal. Ten years later the Appalshop possessed a unique and invaluable inventory of 30 documentary films.

The Whitesburg center has also expanded cautiously to include a recording operation, a theater, a periodical and a photography workshop. At present about half the annual budget comes from sales or rentals of Appalshop productions, with the remaining half split about equally between private donations and government grants, principally from the two national endowments, the Kentucky Arts Commission and the federal Economic Development Administration.

Chester Cornett possesses enough personality to justify the Appalshop's first feature-length expansion. Curiously, one of the newer shorts, "Oaksi," a portrait of Oaksie Caudill, a basketmaker from Letcher County, Ky., tends to dry up within 22 minutes because the subject himself is too taciturn and placid to hold the camera as Cornett does. Cornett's slightly crazed chipperness transforms "Hand Carved" into a remarkably sustained series of priviledged moments.

Cornett's personal idiom is often beautifully reinforced by the clean, alert camera work. "You can't make 'em by a pattern," Cornett remarks. "I got 'em in my head, and that's how you gotta make 'em. Now we use this here-un for the pattern on this here piece of wood." The camera is right where it belongs, the cutting crisp and astute, illustrating the self-description. Similarly, Cornett's analysis of his homemade measuring technique is supported by flawless cinematic observation: "I cannot do a good job with a carpenter's square. I'm a handmade. I do all my measurin' with my hand and my thumb. Two hands and one thumb is what I call 13 inches.

Smith and the Appalshop can be proud of their own handiwork. "Hand Carved" is a lovely machine-made tribute to fading handmade craftsmanship.