A new layer of glass designed to protect against attack with a hammer or handgun now covers the original copies of the Constitution, the Bill of Rights and the Declaration of Independence, National Archives officials said yesterday.

The glass was installed Tuesday night as a result of an attack in October by a man who struck the documents' display case twice with a hammer, according to Susan Cooper, a spokeswoman for the archives.

The upper layer of glass was damaged in the attack, but the documents, which are sealed in helium-filled cases of glass and bronze, were not harmed, she said.

Since the attack, the documents have remained on display, protected by a temporary glazing.

The new covering is a laminated glass similar to that used in automobiles and buildings, Cooper said. "I can't tell you how thick it is or how much it weighs for security reasons," she said.

Randall Husar, 37, was found innocent by reason of insanity in the attack. A federal judge ruled Monday that Husar should remain confined to St. Elizabeths Hospital.

Visitors to the National Archives do not pass through metal detectors, although packages and handbags are checked by guards.

"Our guards are much more vigilant than they were, more sensitive to security problems," Cooper said.