Which practice is NOT recommended for caring for spare parts?

Allowing free movement on the shelves is not a recommended practice for caring for spare parts because it can lead to damaging incidents. Spare parts that are allowed to move freely may become susceptible to impacts, collisions, or falls, particularly in environments where vibrations or movement occur. This can result in physical damage to the parts, compromising their effectiveness and reliability when needed.

In contrast, the other practices mentioned are beneficial for the longevity and integrity of spare parts. Storing in a dry environment helps prevent corrosion and deterioration, especially for metal components. Using vibration isolation pads protects sensitive parts from the damage that vibrations can cause. Tying down the shafts secures them in place, preventing movement that could lead to misalignment or damage. All these practices contribute to maintaining the quality and reliability of spare parts, making it easier to deploy them effectively when necessary.