I have an old DIY book, originating from I guess from the twenties, mine's printed in '57. It says you can magnetize a tool by sliding it against a strong magnet. How come, when I needed a magnetized screwdriver, I had a handful of strongest magnets I have so far seen, taken apart from broken hard drives. Just a few strokes will keep my screwdrivers magnetized for months, strong enough to pick up half a dozen computer screws. I guess they would last even longer if they weren't in a single pocket in my toolbag interfering each other.