Final answer:
Magnetic field lines can be mapped out using a compass or iron filings. The lines indicate the direction of the magnetic field.
Step-by-step explanation:
Magnetic field lines can be mapped out using a small compass. The compass is moved from point to point around a magnet, and at each point, a short line is drawn in the direction of the needle. Joining the lines together reveals the path of the magnetic field line. Another way to visualize magnetic field lines is to sprinkle iron filings around a magnet. The filings will orient themselves along the magnetic field lines, forming a pattern.