Leave the hand grenades -- real or fake -- and other forbidden items at home, the Transportation Security Administration said Tuesday as a reminder to millions of travelers expected to fly over the Thanksgiving holiday.

Knitting needles are OK; fireworks and dynamite are not. Meat cleavers and swords are allowed on planes, but only in checked luggage.

"The trendiest thing so far this year has been credit card knives," said Camilo Bernal, a TSA officer working at Kennedy Airport.

These and other prohibited objects -- including replica and toy guns as well as household products such as bottles of Liquid Plumr and cans of flying insect killer -- were discovered in passengers' carry-on bags or in their checked luggage in the past three months alone, TSA officials said.

Bringing a handgun or a silencer on a plane will land you in jail, said Paul Leyh, a federal security director at Kennedy.

That's what happened to a Port Washington man Tuesday morning when he tried to slip a gun silencer through security at LaGuardia Airport's Central Terminal Building, according to Joseph Pentangelo, a spokesman for the Port Authority, which manages New York-area airports. The man was charged with third-degree criminal possession of a weapon, Pentangelo said.

Fewer guns are found at New York-area airports during check-in compared to other airports across the country due largely to stricter gun-control laws in New York and New Jersey, Lisa Farbstein, a spokeswoman for TSA, said.

As of September, 1,855 guns have been discovered by TSA officers at airports across the nation, but only a total of eight were found at Kennedy and Newark Liberty International Airport, Farbstein said.

During the coming 12-day Thanksgiving travel period, Farbstein said more than 25 million passengers nationwide are expected to fly, a 1.5 percent increase from 2013.

Each year, passengers surrender 12 tons of goods at Kennedy, LaGuardia and Newark airports.

Among some of the banned items on displayed at Kennedy Tuesday were corkscrews, scissors and knives. Then, there were two perfume bottles shaped like grenades.

"You're not allowed to take something like that," said traveler Scharnell Morison, 27, of Cape Town, South Africa.

Malisha Crespo, 34, of Patchogue, who was waiting at Kennedy yesterday for a flight to Trinidad to visit family, couldn't believe the stuff passengers try to slip past checkpoints.

"We just have clothes, jewelry and shoes and some cleaning products -- nothing metal at all in my suitcases," said Crespo, who was traveling with her 9-year-old son and grandmother.

If a traveler is unsure what is permitted and what is prohibited, TSA has an app for that.

The most common question air travelers have is what is a liquid.

"If you could spill it, spread it, smear it, squeeze it, spray it, pump it, and pour it -- it's a liquid," security officer Leyh said.