The Web, he said, " became a virtual wall that anyone was free to write on, however they wished.

The on-line gallery has five virtual walls (not in 3-D) that display two works each.

I pointed at the virtual walls, to show Lucy what I saw.

The Web allows almost anybody to nail a broadsheet to the virtual wall for all to see.

The most aggressive districts are erecting virtual walls around their schools, as if trying to keep the outside world at bay.

A virtual wall of brush had stopped his stampede.

As they rode slowly toward a virtual wall of trees, Kirk was struck by their awesome beauty.

No longer staccato, the rain was a virtual wall of sound slamming against the building.

One side was a virtual wall of rock and thick foliage, the other an abyss.

But now virtual walls join bricks and mortar as means by which countries protect themselves from outside threats.