Technicians called "goopers" spray on a quarter-inch layer of rubber, providing more softness and pliability.

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When you press a key on these models, its underside squishes through a layer of rubber that touches a circuit board.

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"A little layer of rubber -- it will protect you from a stone or a glass, but a nail could puncture that, " Thompson said.

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In the early 19th century the Scotsman Charles Macintosh developed a process for making waterproof fabric by putting a layer of rubber between two layers of cloth.

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When pressurized water is fed over such an intersection, the pressure pushes down the thin layer of rubber, separating it from the fluid below, and it clamps shut the fluid channel below, like stepping on a hose.

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