WARNING!!!! DANGER!!! Rear Projection TV Screen.

The Rear Projection TV sets used a Fresnel Lens as part of the front screen.

 DO NOT LEAVE THEM WHERE THE SUN CAN DIRECTLY HIT THEM.

True stories: A couple of techs have left them on the customers bed while servicing the sets. (The lens are plastic and scratch easily).
 The sun hit the lens and set the beds on fire.
 (Not exactly what you want to have happen in a customers home!).

One shop owner I personally knew had several of them laid against a pine tree outside their shop.
 The sun hit them and the pine tree caught fire.  They could have lost their business to the tree fire!

That event made it to the tech net I was a member of. We all had a chuckle, but it was a severe warning too.

They are useful for projects, but please be careful with them.