ONE WAY TO find out what is cooking in local kitchens is to watch Frank J. Monaldi Sr. sharpen knives. Monaldi is a grinder. He puts keen edges on scissors, saws and garden tools. Customers drop these items off at the shop behind his house on White Avenue in Northeast Baltimore. But the bulk of his business, called Frank's Cutlery Service, is sharpening knives.

Once a week he stops by some 150 area grocery stores, delis, cafeterias, businesses and restaurants to scoop up dull knives and replace them with freshly sharpened cutlery.

The other morning, for instance, he was sharpening knives retrieved from the Maryland Wholesale Seafood Market in Jessup. As the grinding stone turned, he picked up a couple of knives with long thin blades. These, he said, had been busy preparing a summertime delicacy, soft-shell crabs, for market.

"These are fillet knives, but the slang for them is 'pig-stickers,' " Monaldi said. He explained that years ago the knives, with their long, skinny blades, were used to dispatch pigs sold at market. Now the live pig markets are gone, but the pig-sticker lives on as the ideal knife to clean a soft crab, he said.

He pulled out another set of seafood-market knives. These had thick blades. They were called "head knives," he said, and were used to slice the heads off hake, rockfish, red snapper and other assorted fish that are sold in Baltimore-area seafood markets.

In the summer, he said, the demand is high for sharpening head knives, pig-stickers and the occasional "watermelon knife." He showed me the latter, a 14-inch-long butcher knife he was sharpening the other day to deliver to the watermelon man in the produce department at Eddie's grocery store on Eager Street.

Monaldi, 51, has been sharpening knives since he was a teen-ager, when he was taught the trade by his uncle, Pio Vidi. The family has a history of making rough edges smooth. Back in 1913 Monaldi's great-grandfather, Pietro Vidi, worked out of the back of a horse-drawn wagon that rolled through the streets of Baltimore, stopping and sharpening tools at appointed rounds.

Monaldi said he "fell" into the sharpening business. After graduating from Mervo high school (Mergenthaler Vocational-Technical High School) and taking a tour of duty in Vietnam, Monaldi returned to Baltimore in 1975 and took a "temporary" job sharpening tools with his uncle, who was ill.

Monaldi has been at the grindstone ever since and runs the business by himself with occasional help from his brother, Mario, who does some deliveries, and from his son, Frank Jr., who is a specialist at sharpening circular saws.

Monaldi's main interest is in the dull knives of Baltimore, Baltimore County and Northern Anne Arundel County. If customers in Carroll or Harford counties need something sharpened, Monaldi says he refers them to his cousins David and Paul Vidi, who operate Vidi Cutlery. "That's too far away for me," he said.

The metropolitan telephone book carries listings for 10 sharpening operations in the Baltimore area, but Monaldi said that the bulk of the area sharpening business is carved out by four outfits: his own, his cousins' operation, the Grinding Company of America and Martello Knife Service.

As a one-man operation, Monaldi tries to hold his share of the market by offering personal service. He carefully plots his weekly routes, trying to avoid "the traffic lights on Moravia Road; they are out of sync." He seeks out the lights on Calvert Street. "They are the best in the city. If you go 25 miles an hour, you will make every light." He also allows himself time to socialize with customers. "I have a joke for every kitchen," he said.

While Monaldi will sharpen a knife or two that is owned by a chef, most of his business consists of sharpening knives that he has leased to a kitchen. The kitchen pays a weekly fee for use of the knives and for having them on point. Most kitchens have two sets of knives, so one set can be slicing while the other is back at the shop being sharpened.

To keep track of which knife goes where, Monaldi employs the box system. Knives destined for the kitchen at Marconi's restaurant, for example, go into a long narrow cardboard box labeled "Marconi's." When Monaldi pulls his van into the alley behind the Saratoga Street restaurant, he carries the "Marconi's" box of sharpened knives into the restaurant kitchen and grabs the other "Marconi's" box, this one filled with dull knives.

Monaldi puts other things in the boxes as well -- bills, notes to himself, or security badges that he needs to get past a guard at a gate. Since Sept. 11, carrying knives in and out of kitchens in downtown office buildings has become a much more cumbersome process, he said. "I used to do my downtown stops in about an hour and half; now it takes me three hours," Monaldi said.

Often, he said, when he is back at his shop, he will open a box of knives and remember a bit of conversation or a joke someone told him when he picked up those knives.

Replaying those stories, he said, is one way he fights the boredom of running hundreds of knives on the grindstone, then smoothing them on a honing stone.

"The advantage of this job," he said, "is being your own boss, and getting out and meeting people. The disadvantage is that you don't get any medical benefits, and it can get tedious."

To keep himself amused he has installed a boccie ball court in the yard behind his workshop. Often, he said, he will fetch dull knives in the morning and sharpen them all afternoon. Then, in the evening, he will play boccie ball in his back yard with friends. On weekends, he plays the drums in the Monaldi Brothers Band.

Over the years, he has seen changes in the food business. Restaurant kitchens, he said, are much cleaner now than they were 30 years when he accompanied his uncle into the back rooms of restaurants.

Knives have changed as well. Stainless-steel blades with plastic handles have replaced the all-carbon blades with wooden handles that once dominated the trade. Health regulations have pushed the movement to stainless steel and plastic, he said.

There is a seasonal rhythm to the sharpening business, he said. As summer fades, so will the demand for soft crabs and sharp pig-stickers. As autumn approaches, hunters will send him deer knives, and weekend foresters will want chain saws sharp and ready for backyard duty.

In the meantime, Monaldi, a grandfather of four, will squeeze in a short vacation at Ocean City with some of the grandkids.

But even on his days off, he has his eyes on the blade. "When I go out to eat at restaurants," Monaldi said, "I always glance in the kitchen and look at the knives."