Materials like the popiscle stick that allow magnetic lines of force to pass through them are called nonpermeable. The force lines coming from the pole of the magnet do not pass through the metal strap. Instead, they are gathered in, travel down the metal strap, and re-enters the magnet at the other pole. Materials that gather magnetic lines of force are said to be permeable. Only magnetic materials are permeable.
Scientists model magnetic forces using field lines.
A compass lines up along a field line, so you can trace field lines with a compass. Iron filings also line up along field lines. Field lines are defined as coming from the north pole of a magnet and returning to the south pole. Magnets have field lines that exert a force on magnets or iron. If there are no field lines, there is no force, the result is magnetic shielding.