• I only work when you're sitting down.
• I can be put together in a snap.
• My length is adjustable.
• Despite my name, I don't hold up your chair.
• I always sit in your lap when I'm at work.
• I am now available for dogs as well as people.
• My image is illuminated in airplanes.
• I can save lives.
• Most cars have at least four of me.
• U. S. law requires use of me.

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Answer:  tleb taes  (read from right to left)