I would assume something like this:
http://www.sears.com...ku=03415367000P
Lights like this are VERY bright, and easy to handle.
I remember watching a Discovery or Travel Channel episode years ago on what a miantenance crew goes through to inspect a wooden coaster. They would use a hammer to hit the track and listen for certain sounds (i.e. deep sound=solid, short sound=loose). They also knew what problem areas had loose nuts and areas that need to be inspected closer than others.
It was a very intresting show. Sorry I couldn't give you more info.
Here's a video on how they inspect a ride...http://www.youtube.com/watch?v=x_oaGXcdWgs