Contact between water and walls may damage them by creating cracks, breaking cement-paint bonds and creating dark-spots on the wall, etc.

The agency cited the barrier there, saying the red band created a "sense of movement on the wall" and reduced its "apparent mass."

He said he would open up what had been a narrow door into the long, narrow kitchen, creating a wider opening on the angled wall, with no door.

A single candle had been lit on the bedside table and it created diffuse shadows on the wall.

All of the points in the scene do that at the same time, so an entire image, in focus, is created on the back wall of the room.

The lighting also creates long and eerie shadows on the rear wall that comprises nearly half the painting.

The art consists of historic petroglyphs created on the back wall of a rockshelter, within an area of 20 feet by 4 feet.

Another has you moving a light source to create a certain shadow on the wall.

The complicated shapes of the spindles and hooks of both varieties created an interesting pattern on the wall.

"It is believed that water entering through these openings is creating pressure on the lower wall, forcing it to bow out," the letter said.