Police call them "the rooftop burglars."

Since January, they have burglarized at least 15 restaurants in Washington, gaining entry through the roof after hours and cutting alarms and telephone wires, according to D.C. police.

Their method, police said, is both distinctive and professional.

Police believe the thieves are usually acquainted with their target. In each case, the burglaries have occurred on week nights after midnight, when the business was closed. The burglars sometimes move from the top of one building to another to reach a restaurant, thus earning their nickname, and usually enter through a second or third floor skylight. Phone and power lines are always cut. They are careful to leave no fingerprints.

Once inside, the thieves usually loot cash registers and safes where they assume the proprietors are keeping enough money to open for business the next day. In a few instances, they have taken credit card vouchers and electronic equipment that some of the restaurants use for broadcasting football games.

But, police said, the burglars have never tried to take any wines or bottles of whiskey and they have never ransacked the restaurants. For those reasons, police believe more professional thieves, and not a gang of youths, are responsible.

Among their victims are the Dancing Crab at 4611 Wisconsin Ave. NW, the Roma Restaurant at 3419 Connecticut Ave., and two adjacent restaurants at 223 Pennsylvania Ave. SE, Jenkins Hill and Yolanda's.

Yolanda's, which is located above Jenkins Hill and is operated by the same company, has been broken into twice, according to manager John Norris.

"Both times, they took nothing, nada," Norris said yesterday. "I guess we've been pretty lucky."

The first incident occurred Feb. 18. The intruders entered through a third floor skylight and clipped the telephone wires, but found no cash. The next break-in occurred three nights later; this time, the intruders gained entry by ripping the bars from the window of Norris' third floor office.

"Again, they didn't take a thing," Norris said. "I keep the wine stock in there and they didn't touch it."

The department is offering a $1,000 reward for any information, which would be kept confidential, that could lead to the arrest or indictment of anyone involved.