The room is completely dark and silent, save a noisy film projector which rattles as its shoots an image onto a blank wall.

On the wall, tiny figures race up and down a field, gathering together, lining up, crashing into each other, and gathering together again. By the projector sits a lone figure--clipboard and pen in hand--periodically stopping the film and running back a particular play or sequence.

The time is any day during the football season, the place Harvard's Dillon Field House, and the films are of the Crimson's upcoming opponent. The figure sitting at the projector is any of Harvard's half-dozen assistant coaches.

For the most part, the coaches aren't looking for anything in particular. Sure, they want to categorize the opponent's offense and defense. Does the team play a 4-3 or 5-2 defensive set on passing downs? Does it usually run or throw on third-and four? Does the secondary play deep zones or man-to-man on first down?

The professional eye notes the answers, and jots them down. The next day, the information will be conveyed at team meetings.

But more than anything else, the coaches are probing for a weakness, any weakness, that will give Harvard an advantage on the field Saturday. Maybe it's a right guard who lines up too far from his center, allowing possible penetration. Maybe it's a quarterback who always uses a quick cadence on pass plays.

The weaknesses are subtle, nearly hidden. Yet they are almost always there. And on game-day, a single weakness, a single flaw picked up by some assistant coach during his hours of game-film watching, can mean the difference between victory and defeat.

Ivy League teams exchange a pair of game films the week before they meet. The arrangements for nonleague games are less standard, but always present in some form.

"We study the films very intensely," Harvard assistant Coach Bob McCarthy says.

Before Harvard's season-opener at Columbia two weekends ago, some Harvard assistant coach noticed a weakness in the Lions' line blocking on punts. The problem was duly noted, passed along, and catalogued. It was stored away, to be recalled at some time during the contest.

In the middle of the second quarter, Harvard had a 14-0 lead but certainly did not have the game locked up. Suddenly a Columbia double-reverse backfired, and the Lions had to punt from their own endzone.

The Harvard punt rush pressure, which up to this point had been ordinary, suddenly exploded. A group of players broke through the line, exploiting the weakness. Kris Thabit reached Lion kicker Al Pollard and intercepted the kick with his stomach. Teammate Mike Hirschland recovered the bouncing ball, and danced five yards into the endzone. Harvard led 21-0, and never looked back.

"That was the critical point in the game," Columbia Coach Larry McElreavy admitted after the Crimson had completed a 35-0 blanking of his squad.

The next week, the same thing happened. Northeastern used a "tight punt" formation, with three link blockers, instead of the standard two, positioned between the line of scrimmage and the punter.

Again the films were studied. Again a weakness, a potential weakness at least, was discovered, noted, and stored away.