Used to work in an electrical wholesalers, there was a engineering firm over the road. They used to send their apprenticies in with a flourescent tube and would get them to ask us if we could fill it up with Light for them!!!

And they told them to keep the tube level or all the light would fall to one end!!

Cant remember the amountof times we watched a lad walk back to the enginering place with the tube level and his workmates ripping it out of him !