Terry, my copper gas line was exposed under the trailer, but I have since removed the stove and furnace
along with most of the gas line and don't remember if it had any damage. Like Darwin says, copper line is now available with a sheath or covering on it. When I worked in the propane
and fuel oil business 20 some years ago we did not have that product available. Now it seems to be standard use for both propane and fuel and certainly what I would use if I was to run new line. Also with either fuel you use flare fittings, NOT compression fittings and check every connection for leaks
. Best to use a manometer when checking propane, but at least use soapy water and watch for bubbles. There was a commercial liquid product for checking for leaks
but it's basically soapy water. Someone suggested a shield of some sort to protect exposed copper lines but be sure to avoid any possibility of vibration or rubbing areas that could wear through the line.