Len Cariou is an actor the way other men are master craftsmen. He trained in the provinces, worked his way up to the big cities and continues to polish his craft. Like other fine craftsmen, he leaves his job behind when he goes home -- a good thing considering that Cariou's roles have included such larger-than-life characters as Sweeney Todd, King Lear, Teddy Roosevelt and now Supreme Court Justice William O. Douglas.

"I've trained myself to give up parts easily," says Cariou, who is starring in "Mountain" at Ford's Theatre through Oct. 28. "It's better to leave it at the theater than carry it around. You bore people to death that way."

Not that there aren't similarities between Cariou and Douglas -- the generally liberal politics, the burly hulking profile, even the tendency to marry again and again (in Douglas's case, four times; in Cariou's, three, plus two well-known romantic liaisons with actresses Lauren Bacall and Glenn Close).

Although part of the attraction to the role was what Douglas stood for, what really drew Cariou to the part was that it was "eminently actable." "Primarily, he was a fascinating human being," says the actor. "Obviously he was a tortured creature in parts of his life -- but he was a brilliant and passionate man."

Cariou, 51, who won a Tony in 1979 for portraying another tortured character, Sweeney Todd, loves that kind of challenge. "It's very compelling to an actor -- it leaps off the page," he says. "You can take the role in five or six directions, whittle them down, and then your vision becomes the play."

That kind of participation in the creative process appeals to Cariou. It was something he enjoyed doing in "Sweeney Todd" and in "A Little Night Music" -- both Stephen Sondheim musicals. "There is great value in creating something for the first time," he explains. "It's a collaborative effort that as an artist you really look for opportunities to do -- especially if you get an excellent result."

In "Mountain," Cariou, working with director John Henry Davis, helped cut the play to two hours, and also helped think out the staging. The author, Douglas Scott, had already crafted the current version out of a much longer early draft, and then cut 20 minutes out of it. When additional cuts seemed desirable, Scott threw up his hands and gave in to Cariou and Davis's suggestions. "In a new piece, as an actor you're listened to," says Cariou. "Any director with brains will say, 'You do it the way it should be done.' "

Cariou took the part partly on instinct. He'd been sent the original version several years ago, at that time a dramatic monologue, but was busy. He sent it back with regrets. When the reworked version was sent to him three years later, this time with two other parts added (for virtually all the men and all the women in Douglas's life), he interpreted its reappearance as an omen. "I figured it was something I should do," he recalls. "We were meant to do 'Sweeney Todd' in '76, but we didn't do it until '79. When those things happen -- so much can happen in the intervening years after all -- it's usually been a good experience."

Another reason to take on the role -- his concern that the country remember what Douglas stood for -- became stronger in the doing. "It was too good an opportunity to pass up, especially when Justice Brennan retired. All the issues he raises in the play are germane today -- the First Amendment issues, the privacy concerns, obscenity, Roe v. Wade, all the things they talked about at the Souter hearings. It turned out to be a much more political play than I thought it was. People should be reminded of what Douglas did."

So although Cariou had first discussed a tour starting in the spring, when given an opportunity to open the play in Washington on the first Monday in October, the same day that the Supreme Court opens each year, he leapt at it.

The conservatism at large in the country today -- in particular the attack on the National Endowment for the Arts -- has a resonance with Cariou. He feels the threat so strongly that at each New York performance of "Mountain," a flier was given out, urging the like-minded to register their feelings with an 800 number.

The support he brings to this position is in part a gesture of solidarity with the artists' community. But it is also the reaction of a man who has participated in the grantmaking process (Cariou sat on an NEA challenge grant panel for regional theaters) and who learned, during the year that he was artistic director for the Manitoba Theatre Center in Canada, what raising money for a regional theater is all about.

But at Manitoba he had to raise only 17 percent of his budget. At the Guthrie Theater in Minneapolis, where he has appeared frequently throughout his career, there was a staff of year-round volunteers that did nothing but raise money. "The regional theaters in this country are the lifeblood of the theater," he says. "And the NEA grants are the basis on which you go to the community and say, 'Can you match this?' It's a crucial resource."

Cariou prepared for his role as Douglas by doing research -- reading biographies of the justice -- and by traveling across the country to see the important places in Douglas's life -- off-the-beaten-track places like the Yakima, Wash., mountains, so that Cariou could envision the hills that Douglas pulled himself up and down as he recovered from polio.

But of course it was a journey of the imagination as well. "Usually I try to get in touch with a character emotionally," says Cariou. "For Sweeney Todd, all I had to do was know a little bit about English history, and for some parts you don't need to research them at all."

His travels across the American hinterlands were natural to him. Canadian-born, Cariou started his stage career in Winnipeg, Manitoba, where his family lived. He says he inherited his lusty baritone from his mother's side of the family ("the Irish side"). All her brothers and sisters were musical, and she wanted her boy soprano son trained as well. (Even today, Cariou is careful to continue his vocal training -- usually in response to the needs of a role.)

From Manitoba, where he came under the influence of the founder of the Manitoba Theatre Center, John Hirsch, Cariou moved to Ontario's Stratford Festival when Hirsch did. And from there he moved on to the Guthrie Theater and to Connecticut's Stratford Festival and Broadway. Although he often returns to the regional theaters, he has been based in Manhattan since 1974, and now lives there in an apartment with his wife, Heather Summerhayes, who also appears in "Mountain."

One of the unusual things about Cariou's 30-year career is that -- like that master craftsman -- he has always kept working. "Mountain" will help him maintain that habit. Staged on a simple set, with only three characters, basic costumes and props, it is the kind of theater piece that can be staged whenever there are gaps in his schedule. It is not too long, or even too strenuous. "Happily it invigorates me," says Cariou, who has a first-refusal agreement with the producer of "Mountain" for the next five years, an obliging arrangement because it offers a vehicle for Summerhayes as well.

At this point, he knows the role cold, so not too much preparation is required. And he and Summerhayes can have a civilized life on the road, working out at local gyms to stay in shape, checking in with local cystic fibrosis chapters (because two of her family members have the disease, she is particularly active in raising funds to combat cystic fibrosis), and playing golf wherever they can find a club.

He is pretty passionate about his golf. "It's a terribly frustrating game," he says. "The challenge is that you are playing against yourself all the time, so the potential for improvement is always there."

Like acting?

"Yes," he says. "It's a learning process all the time."