WHEN YOU visit the National Gallery you can always pick out the part-time summer guards. We're the ones with the baggy uniforms and the funny-looking shoes.

I'd been out of work for more than a year before I was hired by the Gallery. A guard job was one of the few in the city that I wasn't overqualified for, and I was happy to have it.

The only part of the uniform you must supply yourself is the footwear. I was extremely strapped for funds, so I bought a pair of $7 specials from a surplus store. I ended up paying for those shoes evey night, from the soles of my feet to the small of my back. I felt like a true artist, suffering for beauty.

Once on post there is nothing to do but watch. No talking, and any answer to a question is supposed to take 10 seconds or less. Eventually you realize that the only way to stimulate yourself is visually - and you're surrounded by pictures.I learned a lot about art that I never would have gotten any other way by this force-feeding. I particularly enjoyed the American collection in the old building and the Small French Paintings in the new East Building. There are bound to be rooms you don't like at all. For my part, if I ever see another fatuous madonna or benign baby Jesus, my faith will be shaken.

But after you've seen all the art about three times the job get duller, approaching terminal bordom and mind death. Time can pass incredibly slowly, especially if your feet hurt. Nights when few visitors came through were the worst. People-watching was the only facetof the job that never dulled.

Watch them - and don't let them touch. A few standard retorts after a guard cautions a patron about touching the pictures are:

"Hey, are you trying to embarrass me in front of my friends?"

"You ain't got a gun so I dont care."

"How else can you appreciate the art?"

The guards were asked to work overtime for the opening of the East Building. I needed the money so I readily agreed. The building is beautiful, a true pleasure to see and be in. But it was clear to me, as the ignored observer, that the major attraction at the opening was not the art, but the people who went with it.

These invited guests were so obviously full of themselves and who they knew and where they had last met (Acapulco last month, London, Paris, Peking, darling) that it was amusing.

A high-ranking member of the East German delegation had to be asked to keep his hands off a painting in the visiting Dresden exhibit. He replied, "But it's mine. "I ask you, is this socialism?

For guards, the most eagerly awaited moment of the day is quitting time. Visitors are cordially informed that it is time to go, and by the time the building is cleared, we part-timers were chomping at the bit to be gone.

Opening-night guests were often slow about leaving, and one evening a slightly tipsy ambassador and his wife were even slower than most. A lieutenant asked them to please move ambassador's wife snapped into action. "Stop it, Stop it," she said, as though talking to a naughty dog. "I'm going right upstairs to talk to Mr. Brown. This is the first time all night someone has been rude to us. The ambassador will move at his own pace."

The result was the slightly tipsy ambassador weaving through the gallery, indeed at his own pace, while a growing crowd of guards piled up behind him, laughing, pointing and removing ties, jackets and shirts in preparation for the made dash to the locker room.

I think my favorite moment of all took place in the spring, during the Bullets playoff series. One of the guards came into the locker room and announced:

"I'll see you turkeys later, I'm leaving early tonight. Me and my baby had a big fight last night and I told her we were through. Well, today she called me at work and said she didn't want it to be over. She still loves me and to prove it she has two tickets to the Bullets game tonight at Cap Centre. So I'm going to leave work early tonight and meet her at Cap Centre and see my boys play. I'll see you fools later."

At this moment someone in the room spoke up. "You're the fool, friend - tonight's game is in Seattle."

One evening two chaps came into my gallery dressed identically in khaki shorts, alligator shirts, sandals, coca-butter tans and bleached, puff-styled hair. Their conversation went a follows: "Oh, Charles, aren't they just precious? I mean they're so perfect. So fascinating! Completely the opposite of the ugly two-dimensional objects in your apartment!"

Charles replied, "Well Robert, the only ugly two-dimensional object in your apartment is you."

A few oddballs showed up from time to time. A woman came in to the Impressionist section, looked at a Mary Cassatt and declared in a loud voice, "This is a fake. The people who run this place keep all the authentic works in storage. They think no one will notice. Shoddy imitations! It's an outrage." She certainly seemed outraged. The room immediately emptied. Whatever her problem was, no one wanted to hear about it. Neither did I, but I was the only one who couldn't leave. So I heard all about it. I told her I'd speak to Mr. Brown about it the first chance I got.

Another evening, I was stationed in the jewel room of the Dresden collection - guarding the family jewels, as we used to call it. A woman walked in, took a look at the gems and announced, "These aren't real. They're paste, they don't shine." Then she held up her hand and pointed to her own diamond. I must admit it was impressive. "This,? she said, "is real. Just look at it sparkle."

Of course, we guards had supervisors, one of whom used to glide around on special shoes to catch us talking, sitting down or otherwise off guard. I asked one of the regular men how this fellow managed to walk around so quietly.

"Well," said my colleague, "his head's real light, so he don't have any weight pressing down on his feet to make any noise with." It seemed plausible.

I was in the Impressionist gallery one night when a Frenchman walked in and gasped. He hurried about the rooms and came up to me and said, "Why, you have 11 Monets here." And he began to weep.

The most often asked questions were: How much is that worth? What time does the cafeteria close? Where are the rest rooms? It seemed to me that a lot of America was summed up in those questions.

One of the galleries in the new building contains Barnett Neumann's "Stations of the Cross." These are a rather abstract series of paintings consisting mostly of white canvas with vertical black strips. Few of us enjoyed experience in the room, few visitors did either. One guard observed, "The reason he called it "Stations of the Cross" is that after you leave the room all you can say is JEEZUZ KEYRIST."

Another room is filled with Mark Rothko's later works - dark, gloomy gray-and-orange blotches of color painted shortly before his suicide. One of the guards, after spending four hours in the room, said, "I don't see what the big deal with those are, all they look like is a bunch of windows with the shades pulled halfway down. And I tell you what. I don't want to look and see what's inside, either.

It was fascinating to see how peoples' reactions appeared on their faces as soon they walked in. This was particularly true in the new building with its Modernists, Fauvists and Cubists. Most people know they are supposed to be impressed with Rembrandt, but these modern works got some quick, honest reactions. Favorable and unfavorable judgments were often so strong they could be felt as well as seen on their faces.

The urge to touch was often overwhelming, and I got so I could predict who would touch a painting and who would not need too much watching. Little kids were the worst. You always had to watch them. Some people were sneaky and would watch you out of the corners of their eyes until they thought you weren't looking and then would put their hand on a picture. I enjoyed catching them.

Other pictures seemed to drew people to them like moths to a flame. Renoir's "Girl With a Hoop" was one of them. I began to take pleasure in spotting a promising toucher, and stalking them. I'd walk quietly up behind them and wait until their hand rested on picture before announcing, "Please don't touch the art." They were shocked back to reality and a bit embarrassed.

I knew then that it was time to quit.