Pardon me, sir, but your pitchfork is in my pants.

There was only one way to go with a sequel to "Friday the 13th, Part 2" -- not up, but out, right into the audience's kisser. Thus was begotten "Friday the 13th, Part 3 -- 3-D," which is now at area theaters and which delivers by the bucket precisely what it promises: glirpy, slurpy, ghastly gore that doesn't even have the decency to remain on the screen. A last vestige of motion-picture propriety falls.

Actually, the ever-avant-garde Mr. Andy Warhol brought this barrier crashing down a few years ago with his 3-D, X-rated "Dracula" and "Frankenstein" films. Those pictures poured on the grand guignol -- replete with 3-D intestines dangling in the air -- as a spoof of bloody movies. But "Friday the 13th, Part 3" is just about as gory and not meant to be funny, although anyone who has seen the first two films in the series, about mass murders at a summer camp, will have to chuckle when a teen-age girl tells her friend, "Nothing's going to happen while we're all here together."

This is not long before two members of a motorcycle gang are punctured in a nearby barn and an attractive young woman suffers a spear gun in the eye. Earlier, a spike is driven through a woman's head, emerging from her mouth, and a man named Harold gets a hatchet in the chest. A better title for this series of films might be "That's Impalement."

All in good fun? Audiences seem to take it that way. It isn't perceived so much as a frightening experience as a gross-out experience. The audience knows the filmmakers have to top the carnage of the previous film. And so, as is traditional, the most spectacular murder is saved for the last reel. The killer grabs a young jock around the head and squeezes and squeezes until . . . zingo . . . his eyes pop out and pirouette right into the 12th row.

It may be at this point that one gives up all hope of maintaining the proper indignation and just begins to find it all perfectly hilarious.

As in the first two films, randy young teen-agers throw caution to the wind to spend time at infamous Crystal Lake, where that demented maniac-about-town, Jason (played again by Richard Brooker -- what a career!) is still on the loose. Apparently it will take a neutron bomb to stop him, because he proves able to function after being stabbed and garroted and can get around quite nicely with an ax imbedded in his skull.

What may be more shocking than the violence is the way the filmmakers refuse to tamper even slightly with their formula. The plots of all three films are virtually identical. The only sources of suspense are: Which piece of cutlery will the murderer use next; and in what order will the victims be eliminated, until there is but one nubile lass running about and screaming her lungs out? They're so shameless, they even duplicate the fake-out ending of the first film, and that was ripped off from "Carrie" anyway.

Also, the comic relief provided by Larry Zerner as a fat boy named Shelly is so excruciating that occasionally one finds oneself identifying with the killer. Anything to banish from the screen this obnoxious kid who states, but fails to prove, that "being a jerk is better than being a nothing."

Dana Kimmell plays the sole survivor this time, but the screenplay is a little murky on setting the latest ghastly occurrences in time. It isn't made clear whether this film is taking place two years after the previous one or on the very next day. Also, a character who was hacked to death in the middle of the film miraculously returns near the hysterical finale only to be hacked to death again.

As directed by Steve Miner and shot by Gerald Feil, the film's use of 3-D is spectacularly and viciously effective. (Gray-lensed Polaroid glasses are handed out at the door; this 3-D process works much better than that used on recent 3-D TV broadcasts.) Not only sabers and butcher knives are tossed into the movie house, however; there are also such relatively benign protuberances as popping popcorn, a leaping snake and a blue yo-yo. From the back of a van, a hippie reaches out with a joint, and very early in the film the audience gets poked at with a pair of rabbit ears atop a television set. An opening scene of sheets flapping on a clothesline is attractively eerie, and a later shot of a victim sitting on a pier that juts into a pool of water is actually pretty.

The playfulness is so engaging it's really too bad that the gore has to be so unrelenting, but the producers of these films are now trapped in their own excess. You can't say they lack for encouragement. In its first weekend of national release, a Paramount spokesman said yesterday, the film made "so much money it's unbelievable" -- approximately $11 million. And so, "Part 4" is a foregone conclusion, although at the moment the notion of shooting in 4-D seems technically unfeasible. Besides, there are some dimensions beyond which man was not meant to hurl meat cleavers.