He earned his spending money in college as a blackjack dealer in a Reno, Nev., casino. Now he earns his living trying to outslick defensive linemen, whom he equates with the bubonic plague.

He became known as the Vaseline Man two seasons ago. In a game against the Dallas Cowboys, the referee order him to the sidelines to change jerseys. A Cowboy lineman had complained the original jersey was too slick and slippery.

Ah, yes, the tricks of the trade.

"Well, there's . . . " Redskin left tackle Terry Hermeling began yesterday, cutting off the sentence as quickly as a knee injury almost ended his career in 1974.

Then, from behind that well-manicured full beard, with a sparkle in his eye, Hermeling continued: "I don't use Vaseline anymore. I only used it once or twice. You do anything you can to keep the defensive linemen's hands off you because they try to hold you, which disrupts your blocking.

"You know defensive linemen scream about holding all the time. Well they grab your face mask; they grab anything they can to keep you from getting another block. But the referees aren't looking for things like that.You don't look for a defensive lineman to hold. They can use their hands, so the refs aren't looking for it. But a defensive lineman grabbing and holding is defensive holding."

Hermeling did not invent the Vaseline trick. It was passed on by John Wilbur, a guard his teammates called "Betsy Ross" because he sewed his jersey to his pads, the better to prevent opponents holding. He also allegedly put thumbtacks sticking out of the jersey and sawed down his face mask so it would be sharp enough to cut in the days when the head slap was still legal.

"Oh, no, I wouldn't use thumbtacks," Hermeling said. "I'm not out to hurt anybody. I don't know if he (Wilbur) sawed down his face mask or not. But if he did . . . Wilbur was a very intense competitor. He taught me a lot about the game."

So what does Hermeling substitute now for Vaseline?

"Nothing," he said. "I don't need to use anything. I've got my jersey tight enough so it's pretty tough for them to get hold of me."

It is no secret why Hermeling and his fellow offensive linemen have been so successful this season.

The line is working diligently. It has gained strength. It has not been wrecked by injuries, as in the past. And it looks better, too, because quarterback Joe Theismann is doing his job better.

Ray Callahan, offensive line coach, sets three basic goals for his unit each game: two sacks or fewer, a rushing average of 4.1 yards per attempt, three sustained drives of eight plays or more.

Here is the scorecard for four games: a total of five sacks, no more than two in any game; two games with a 4.1 rushing average or better, another at 3.9; only one game in which the Redskins failed to have three sustained drives of at least eight plays.

"I won't say it's all come together yet," Hermeling said. "I'd say we're still improving, still getting better.We're working harder at it and that's what's making things happen.

"Plus last year we started out and were doing fine until George (Starke, the right tackle) got hurt and a few people got nicked here and there. Injuries are the key factor."

Hermeling sees a more mature Theismann this season.

"Joe had his own improvements to make," Hermeling said. "He is staying in there and taking his sets the way they want him to. He's reading his keys and throwing. He's not moving around looking for someone else and improvising on his own which makes it easier for us because we know he's going to be back there in that pocket.

"If you know where your quarterback's going to be, then all you have to do is your job.If Joe doesn't have a receiver open now or a secondary receiver . . . he's either running the ball for yardage or he's throwing out of bounds, which is what a good quarterback does.

"He's playing his percentages instead of taking chances, which is the way the game is supposed to be played."

That Hermeling is playing is a minor medical miracle. He was told that the knee injury he suffered hitting a blocking sled the second day of the Redskins' 1974 training camp would end his career. He tried to come back too soon, and the surgery had to be repeated.

The next season he was put on the "physically unable to perform" list. Then, in mid-October, Tim Stokes, the man who replaced him, was injured and Hermeling came back and played a full game against the Cleveland Browns. Hermeling is now in his 10th season and the Redskins traded Stokes away last year so Hermeling could return to his natural position of tackle.

"I enjoy playing the game," he said, recalling the doctor's advice. "If you're a competitor, somebody tells you something like that -- you're going to try and prove them wrong. I've always overworked it, tried to come back too soon on injuries. That's the basic reason why I had troubles with injuries early in my career."

Theismann, who did not participate in Tuesday's drills because of a slight infection in his throwing elbow, was back at full speed yesterday . . . Cornerback Lemar Parrish has the flu, but he went through some plays . . . Coach Jack Pardee said, "Today and tomorrow are our big days for getting the game plan in. Even though he wasn't at full speed, it was important for him to hear the calls" . . . Defensive end Karl Lorch (bruised foot) and defensive tackle Paul Smith (hip pointer) are listed as questionable for the Falcons.