I need to run a gas line to a floor mounted gas heater but I cannot run it behind the wall. How do I hide the gas line?
You might just have to box around it, if you can mount it right against the wall, fairly low.
If the line is the old black iron gas pipe, you don't have to worry about it getting crushed if something gets dropped on it. But you might have to worry about damage to the connections (and leaks) if something heavy enough is dropped on it.
If it's the yellow (or black) corrugated stainless steel pipe, you might need to be concerned about possible damage to the pipe itself, too.
But either way, your best bet might be to mount the gas line as close to the wall as possible, near but not on the floor, and build a box around it with moulding or plywood.
If it's a hose, you might be able to get away with using one of those carpet runners that you can stuff cables into on the bottom.
If you go with the build-something option, maybe you could create some built-in seating. Build a frame, put some particle board or plywood on top and throw some cushions on.
Or you could make shallow cabinets to hide the pipe and create some useful storage space.
The simplest thing to do is to paint it the same color as whatever it is running next to. It won't completely hide it but it will go unnoticed by some people. Keeping it low and parallel to the floor might help too.
If you're not willing to build anything around it, then also try to take advantage of your layout and furniture to hide it.
Also consider paths where it will run in less frequented rooms or spaces. i.e. run though a closet the out right behind the device.