Bobb McKittrick, who helped the 49ers win five Super Bowls by repeatedly molding lesser-rated players into the effective offensive lines that blocked for Joe Montana and Steve Young, died yesterday after a 14-month bout with liver cancer.

McKittrick, 64, one of the first assistants hired by Bill Walsh in 1979, was third in longevity with a single team among NFL coaches last season. He remained active almost to the end, although last year, he rarely was able to travel to road games and spent his working time primarily studying player tapes in the office.

He was diagnosed with cancer of the bile duct shortly after the 1998 season ended. For a time, McKittrick was on the national list awaiting a liver transplant, but by the time a liver became available for him, the disease had spread too far. He died at Stanford Hospital.

The 49ers honored McKittrick at halftime of a home game against Tennessee last October. After the season, the team invited back many of McKittrick's former linemen for a dinner to celebrate his career. An annual award honoring the 49ers' best lineman is named for McKittrick, whose NFL career spanned 28 years, the last 21 in San Francisco.

``He was the most successful offensive line coach the game has ever seen,'' Walsh, now the 49ers' general manager, said yesterday. ``He was a great man and will truly be missed by all of us.''

A former Marine officer who once planned a career as a teacher, McKittrick was well-read and well- traveled. In his coaching, he relied on players who demonstrated athletic ability and could learn proper blocking techniques.

The theory was a simple one, based on the David vs. Goliath principle. McKittrick believed that smaller, agile athletes could succeed against bigger, stronger men. He frequently showed little or no interest in some of the higher-rated and better-publicized line prospects because he felt they weren't suited to his style, no matter how good they might be.

Instead, he built lines by using undersized players that other teams in the league either overlooked or did not want. For years, the 49ers had the smallest offensive line in the NFL, but they managed to win five championships and construct a dynasty that remained near the top of the league on offense for 20 years.

Walsh agreed with McKittrick's theories, but in the mid-'90s, after Walsh had left the organization, the 49ers got away from that style and began seeking larger men.

Perhaps it was only coincidence, but that was when the 49ers' downfall began. Team officials at the time said bigger linemen were needed because defensive linemen were getting bigger, too.

Yet, McKittrick's theories were proved still to work when the Denver Broncos won the Super Bowls following the 1997 and 1998 seasons with the lightest offensive line in the NFL.

In a 1998 interview, McKittrick succinctly explained his theory.

``I like smart, athletic people who can do schemes and can understand them, instead of just blacksmiths who try to hit it harder the next time,'' he said. ``We do a certain amount of what people in the past have called finessing, and it's very subtle, but the better the athlete, the better they can execute it.''

During McKittrick's tenure as the 49ers' offensive line coach, the team produced 19 Pro Bowl selections among offensive linemen, only one of them a player drafted in the first round.

Bobb McKittrick was born four days after Christmas, 1935, in Baker, Ore. He earned a bachelor's degree in agriculture and a Master's degree in education at Oregon State, where he played football and served briefly as an assistant coach following a three-year term in the Marine Corps.

Originally, McKittrick got involved in coaching because the football job paid $450 a year more than he earned by teaching. He followed head coach Tommy Prothro from Oregon State to UCLA and eventually to the San Diego Chargers, where he first met Walsh, another assistant on Prothro's staff. Walsh left San Diego to coach at Stanford but, two years later, he became the coach of the 49ers and hired McKittrick.

McKittrick was known for teaching his smaller linemen to block low on defensive linemen to try to get them down on the ground. The technique is called cut-blocking or leg-whipping, depending on who is describing it. Defensive linemen hated it, and former Raiders defensive lineman Howie Long, who was voted into the Hall of Fame in January, once tried to attack McKittrick following a game.

``Typically in the NFL, linemen would like to play the whole game standing up,'' Walsh once said. ``They prefer never to have to go to the ground. Well, we went to the ground and we cut people down, and we hit people around the ankles. (Opponents) have not liked that approach.

``There are just very few coaches who were willing to teach those techniques. They're more physical and tougher to execute than everybody standing up and pushing each other around.''

Several former 49ers assistant coaches who left the team to become successful head coaches elsewhere credited McKittrick as a significant factor behind the team's long run of dominance. Jon Gruden, now the Raiders' head coach but once a 49ers assistant for a year, said he learned more from McKittrick than any other coach in the league, calling him ``the smartest coach in football.''

Two Super Bowl-winning head coaches, Mike Holmgren of Seattle and Mike Shanahan of Denver, were trained in the nuances of Walsh's West Coast offense by McKittrick when they joined the 49ers as offensive coordinator.

``He's unique among line coaches,'' Holmgren once said. ``One, he doesn't ever curse, never swears. He's a very bright guy, a voracious reader and writer.

``At the same time, he is really flexible, really a good man to work with.''

That McKittrick managed to last two decades under three head coaches -- Walsh, George Seifert and Steve Mariucci -- while being frequently outspoken says much about his ability to coach. Even Walsh, who tolerated little dissent as a head coach, never succeeded in fully muzzling him.

``In staff meetings, I try to say what needs to be said,'' McKittrick explained. ``If everybody just wants to say what they think somebody wants to hear, after awhile, you get in a pretty sad groove, I believe. Some people have mixed feelings about me opening my mouth.''

Walsh agreed. He said, ``You have to understand him.''

McKittrick also was known for his aversion to cold-weather clothing. During games in the Northeast and Midwest, he used to stand on the sidelines wearing nothing heavier than a short-sleeved shirt, regardless of the weather. Holmgren once told him he had to wear a coat because it was so cold his teeth were chattering and he couldn't be understood.

McKittrick said he simply didn't get as cold as other people, but once he got the reputation for going coatless, he admitted that he enjoyed it because line coaches don't usually get much attention.

It was typical of McKittrick to continue to work during his illness. He went through the 1982 season wearing a colostomy bag because of surgery to remove his colon. The operation caused him to miss the ceremony at which the 49ers received their first Super Bowl rings, but three weeks after surgery, he was on the field coaching at a mini- camp.