For those who have access to old computer harddrives; these drives contain very powerful ceramic magnets mounted on plates with holes (for fixing). Get a length (about the width of a broom) of  2x2, mount as many of these magnets as you can along the length of one side. On the opposite face drill a hole to accommodate a broom handle (at about 75degrees). Attached a wheel at each end of the length of timber and there, you have a magnetic broom that will sweep across a floor and find that missing screw or pick up those slithers of metal in no time. - From Craig, avid reader in Australia.