Most of the magnetic field lines are along the z-axis (up and down) so anyone could still simply slide the hammer towards the end of the metallic floor it's sit

Most of the magnetic field lines are along the z-axis (up and down) so anyone could still simply slide the hammer towards the end of the metallic floor it's sitting on(like the sewer cover) and be able to pick it up then. That's how we unstick really strong magnetic targets in our sputtering system, we simply slide them off.