Israel calls it a "security fence" or "peace line," aimed at blocking suicide bombers from the West Bank. Palestinians call it the "apartheid wall" or the "new Berlin Wall," aimed at isolating them and stealing their land.

	Online Graphic Click here to download a .pdf file about Israel's Security Fence and other international barriers. You must have Adobe Acrobat Reader, available as a free download from Adobe. Related story Israeli court halts fence

Whatever its intent or effect, the controversial barrier that got Israel hauled into the International Court of Justice in The Hague last week defies popular definitions of fence or wall. It is a state-of-the-art security system, and it is part of an international boom in barriers designed to protect power plants, chemical facilities, gated communities and, increasingly, nations.

"When you mention 'fence,' people think of a chain-link fence around the playground or the picket fence in their backyard," said Allan Topol, an expert on security barriers who provides analysis for Military.com, specializes in international law at the Washington, D.C., law firm of Covington & Burling, and writes best-selling spy novels like "Spy Dance," which was set in the Middle East.

"Israel's security fence is something else," Topol said. "It's an engineering tour de force."

It also represents what seems a growing international acceptance of the famous line from Robert Frost's "Mending Wall" that "good fences make good neighbors."

Some of the other more prominent projects now under way or being contemplated:

Saudi Arabia is building an $8 billion security barrier along its border with Yemen to block the entry of smugglers and al-Qaida operatives -- a barrier that might eventually be extended to surround the entire country.

India plans a vast security fence to keep terrorists from crossing the Line of Control, the border between Indian and Pakistani-administered portions of the disputed state of Kashmir.

Botswana has erected electrified fences along its border with three other African nations to stop infiltration of refugees and hungry livestock.

The European Union is funding the construction of security fences in Spanish enclaves in Morocco to stem illegal immigration from Africa into Europe.

The United States may have planted the seeds of the modern boom in security barriers. In the 1990s, it began building a security fence to seal off illegal immigration through its leaky 1,920-mile border with Mexico.

California, citing concerns about the barrier's environmental impact, moved two weeks ago to block the federal government from completing the last stretches of the fence near San Diego.

Big international border barriers go way back, however.

Among the more famous were the 4,500-mile Great Wall of China, Earth's longest structure; Hadrian's Wall, which the Romans built to keep barbarians out of Britain; France's Maginot Line, designed to block German forces before World War II; and, of course, the Berlin Wall, which was built to keep Germans from communist East Germany from crossing into democratic West Germany.

The Israeli government began writing the latest chapter in the history of notable walls in 2002 when it approved what is officially known as the Security Fence.

First envisioned as a relatively modest $120 million project, the Security Fence has evolved into what may become the biggest and most costly construction project in Israel's history.

If completed as planned, the Security Fence would cost more than $1.3 billion, twisting and turning for more than 400 miles from Jenin to Hebron, completely separating Israel and certain Jewish settlements on the West Bank from the West Bank's Palestinian majority. That's longer than the main line of the Pennsylvania Turnpike, which stretches 359 miles from the Ohio border to the Delaware River Bridge.

"The Security Fence is the biggest infrastructure project in Israel," according to Israel's Ministry of Defense. "As such it uses a lot of the existing infrastructure resources."

Some two dozen contractors and more than 6,000 workers are building the fence on tight time schedules. Contracts call for the immediate replacement of any company that falls behind deadlines to complete each mile of fence, which now runs more than 120 miles. Another 120 miles is to be finished this year.

Each mile of fence requires the excavation of 230,000 cubic yards of soil; the laying of 12,000 square yards of asphalt, and the installation of 80 sensor-detector posts, 600 anchor posts, 6,000 square yards of wire fencing, 26,000 yards of barbed wire, and truckloads of other material.

All that effort is needed because the Security Fence is a carefully engineered series of barriers to infiltration, costing about $4 million per mile. The project combines fences, ditches, patrol and "trace roads," concrete walls, barbed wire, watchtowers, cameras, electronic sensors, military checkpoints and gates where people and vehicles can pass.

Most of the barrier consists of a concrete foundation topped by 15 feet of wire mesh fence. Protecting the fence on the Palestinian side are rolls of barbed wire and a 12-foot-deep ditch to prevent vehicles from smashing through. A road allows Israeli tanks and armored personnel carries to patrol the fence line.

On the Israeli side, another paved patrol road abuts the fence. Alongside is a dirt "trace" road, topped with fine sand that would reveal intruders' footprints. Grooming vehicles comb the trace road's surface each morning and evening. Another barbed wire barrier runs along the trace road.

About 5 percent of the structure, in areas of high risk, will consist of a concrete wall, almost 25 feet high with watchtowers to protect against sniper fire.

"From a structural perspective, there is nothing outstanding about security walls," said Chris T. Hendrickson, chairman of civil and environmental engineering at Carnegie Mellon University. Security barriers from the Great Wall of China onward always have been relatively simple structures, he explained.

"The only unusual structural issue is what specification to build to -- whether to build a wall to withstand an auto, a truck or a tank ramming into it. Surveillance technology is where much of the innovation is coming in."

The Security Fence bristles with TV cameras, motion detectors and magnetic sensors that watch for intruders. They relay data to command centers that can dispatch troops instantly.

Officials, however, will reveal few details about the sensors, except to indicate that they use affordable intrusion-detection technology -- rather than some sort of exclusive cutting-edge devices.