Hold a soft iron bar pointing to the north and sloping downwards, and hammer it several times. It will become slightly magnetic.The earth is surrounded by magnetic field lines, which meet the earth in Great Britain and North America at an angle between 60 and 80 degrees. When the iron is hammered, its magnet particles are affected by the earths magnetic field lines and point to the north. In a similar way, tools sometimes become magnetic for no apparent reason. If you hold a magnetised bar in an east west direction and hammer it, it loses its magnetism.