WASHINGTON - Dogs can jump through screens and glass. They can break metal leashes and vault picket fences. Then they can bite the suspicious, the oblivious, the young, the elderly. And they go for mail carriers, who traverse their territory daily.

More than 4 million people were bitten by dogs last year, half of them children and 3,475 of them mail carriers, said U.S. Postal Service spokesman Mark Saunders. The frequency of attacks increases as the weather warms.

Hence, National Dog Bite Prevention Week, sponsored by the Postal Service - and this year to be observed May 21-28.

''There are two things people say that are almost always false: 'The check is in the mail' and 'Don't worry, my dog won't bite,' '' said Saunders, patting his dog Chester, an easygoing springer spaniel.

Postal Service employees were counting on that canine excitability last week as they taped a public service video for Dog Bite Prevention Week on Saunders' cul-de-sac in Waldorf, Md.

Given the town's mostly curbside mail delivery, Waldorf doesn't have as many attacks as such dog-bite hotspots as Houston, Los Angeles and Cincinnati, where the week's events will kick off early, with a chorus line of mail carriers showing their scars on May 18.