With his size-10 1/2B right foot all warm and cozy in six socks on a snowy day, Mark Moseley yesterday kicked a last-gasp 42-yard field goal that set an all-time National Football League record and produced a 15-14 victory over the New York Giants that put the Redskins in the playoffs for the first time since 1976. Besides which, it got him off the hook with Santa Claus.

Someone stole Moseley's wallet two weeks ago, relieving him of $800. "So I told him not to buy me anything for Christmas," said his wife, Sharon. "I told him all I wanted were two field goals today. The third, I didn't even ask for."

With his first two field goals against the Giants yesterday in snowy RFK Stadium, Moseley tied Garo Yepremian's NFL record of 20 consecutive field goals set in 1978-79. There were only nine seconds on the clock when Moseley went out to try for his 21st. As always, he patted Joe Theismann on the rump, saying to his holder, "Let's get it, Joe."

Cool.

Cool as Santa making a delivery.

Cool as he'd been around home Tuesday when his three small children asked Daddy to put up lights in the shape of a Christmas tree. Daddy was so cool then he brought out a ladder and with those precious toes climbed 10 feet to the roof.

"My wife saw me up there and said, 'What are you doing? Are you crazy? Get down,' " Moseley said.

"I don't want him to ski, I don't want him to do anything that'll get him hurt," Sharon Moseley said.

Cool. The good kickers like the showdown at game's end. They're cool as gunslingers on a dusty street. Go for your iron, Mac. That's always been Moseley's attitude, born of 11 years of these live-or-die duels. He's won more than he lost. Won so often, in fact, that the cursed Cowboys always ordered officials to check the legality of Moseley's shoe, as if it contained a radar-guidance system and not a heap of bones.

Came showdown time yesterday, though, and Moseley wasn't the cool fellow who says of himself, "Ice water in my veins." He came out for that 42-yard field goal for the record, for the victory, for the playoffs, and he confessed, "I felt my insides churning. For the first time, I was really overly excited about a field goal."

Don't ask what he was thinking. He'll say kickers don't think. Thinking is dangerous. Just kick it. He'd taken off the down-lined slipper he wore to keep his socks dry on the sidelines. For a while, he stood with his foot in a garbage sack. With the showdown at hand, he put on the square-toed shoe that, with all those socks, is so tight it cuts off circulation to the toes that own Washington.

Other kickers warm up by kicking into a net. Moseley kicks at the air. Last thing he does, out of superstition, is half-kneel and jam his toes against the ground to get everything just so inside that 10 1/2B made to his specifications (he files down the rear cleats so they won't snag in the turf).

Other than four words to Theismann, Moseley said nothing. No one said anything to him, either. "Most of the guys were afraid to say anything," he said, because as nice as the record would be for Moseley, the victory is the sweetest part for the team. The Redskins haven't won a playoff game since 1972, and with Moseley's magic they see this season as special.

Of the 21 field goals, 18 have come this year, seven in the last two games, and Moseley's kicking points have been the difference in five of six wins.

Jeff Bostic's center snap on No. 21 was perfect, Theismann's hold was perfect, and Moseley "hit that ball as well as I've ever hit a ball."

That's when he heard something. A little tick. A hand against the ball? Then, he would say later, he heard someone shouting, "I hit it, I hit it."

But Moseley's kick was so strong that even deflected--a Giant confirmed touching the ball with his fingertips -- "it never quivered," Moseley said, "and it went straight through."

There were four seconds left, and there broke out a victory celebration of acrobatic high-fiving that wound up with Bostic lifting Moseley into the gloaming.

"I'm kinda proud of myself," Moseley said. "I was about to lose control, I was so excited. It's a big thrill to take that challenge."

When you're 34, nothing surprises you in the NFL. Moseley was cut his rookie year at Philadelphia, replaced by someone named Happy Feller. At Houston, the coach took him aside in the team's parking lot and told him he had to cut him because he'd had a dream that Moseley wasn't good enough.

Nothing surprises kickers, anyway, for they are a breed apart, soloists in a symphony of sweat. Only a kicker would carry a towel especially to wipe the snow off his toe.

So Moseley found it comforting, not unusual, when he spent this week having premonitions.

"I had the feeling all week it would come down to the record field goal and it would win the game, too," Moseley said. "That's why I was probably more anxious than any game ever . . . " During the third quarter, Moseley said, he went to the team doctor, Donald Knowlan, and said, "It'll come down to a field goal."

Earlier, Moseley missed an extra point kick. He said he had been rushed when he couldn't find an official to hand his towel to, and that he didn't have time to dry his toe. The ball squirted wide.

"That might have been a blessing," he said. "It woke me up. It made me more alert."

By then, Moseley had kicked a 20-yard field goal. Afterward, he would kick a 31-yarder and then the record-setter.