Выражение встречается в следующем контексте:
Magnetic Particle Examination.
Longitudinal Magnetization Technique. For this technique, magnetization is accomplished by passing current through a multi-turn fixed coil (or cables) that is wrapped around the part or section of the part to be examined. This produces a longitudinal magnetic field parallel to the axis of the coil.
If a fixed, prewound coil is used, the part shall be placed near the side of the coil during inspection. This is of special importance when the coil opening is more than 10 times the cross-sectional area of the part.

Если можно, поясните, пожалуйста, что значит "the part shall be placed near the side of the coil during inspection".
Заранее спасибо