If you have equipment/apparatus that is very sensitive to magnetic fields, even as weak as the earth's own magnetic field, it is possible to shield it from this. Magnetic fields consist of magnetic lines of force that from complete loops, that is, no magnetic line of force has an end. Because of this, it is NOT possible (by simple conventional means, anyway) to completely stop such fields like stopping a "bullet". Magnetic shielding, instead, provides a zone or region of space where even strong fields are significantly ("noticeably") weakened and retarded. To provide this, you would surround your apparatus with a single-piece container made of magnetic alloys and metals, like tin. Iron, nickel, etc.

We attempted to include a ruler in these photographs to show that one must place such a toy magnet about at least 10cm or so away from the outside container in all directions in the pane of the containers' openings (certainly not coaxially!). The compass inside should be placed EXACTLY at the center of both containers. This compass must be sitting half-way up the smaller container, which in turn should be sitting halfway up the larger container. The smaller container must be centered within the larger container. One gets the BEST results when magnetically shielding the compass included from the Earth's own magnetic field, rather than that of a closer, more concentrated toy magnet. Also, in general, try keeping the included compass away from any other toy magnets, as this compass can be easily magnetized/demagnetized by them, which can destroy the compass' own, very weak, magnetic field, and ruin its proper function. The results may be typically slight but still easily noticeable and easily measureable, as these containers at best provide only SOME protection. Proffessionals actually use extensively heavier and more expensive magnetic shielding around a small room. Such proffessional shielding will render the contained space inside it almost magnetically neutral for almost all magnetic fields known.

A FEW WORDS OF CAUTION: You must remember that, for the shielding to work well, the magnetic field to avoid must be OUTSIDE the CONTAINER and NOT TOUCHING this container. These containers are very sensitive to becoming magnetized themselves, either by PHYSICAL CONTACT in any way with another magnetic object, or in the presence of an EXCESSIVELY STRONG magnetic field or sufficiently string magnetic fields that are too close to the containers. The container itself must NOT be magnetized AT ALL either. This is "action-at-a-distance, part 5".
In the event that these containers DO become WEAKLY magnetized, there are suggestions (included in the parts/materials list of the INTRODUCTION) on how these containners could be demagnetized.