In a different thread I posted the remark "No knowledge is ever wasted". Recently I discovered how useful my long ago, virtually forgotten secondary education can be useful at times. My poor old laptop, (about 6 years old by now) has had in recent years, a tendency to overheat and switch off at the most inconvenient moments. I thought about the problem for a little while, and in a dim dark recess of my brain, some synapses fired, reminding me of the physics of heat transfer. After a little cogitating, I found a 12" stainless steel ruler that I had acquired for no particular reason, placed a couple of strategically located dobs of blu-tack at either end...and stuck the ruler in intimate contact over the hottest part of the computer...and then directed a USB powered fan to play over the ruler. Overheating problem solved. It sometimes amazes me how useful the stuff that the science teacher was droning on about at the time, has actually been put to effective use.