Magnetic trays are frequently used when screws, nuts, nails and other small magnetic metals are used on a particular task. They can attach easily to any metal surface as long as that surface doesn’t have any electronics nearby, or pose a safety hazard.
When a magnetized tray will not suffice, a small parts bag or container should be used. These containers provide control over the small parts and minimize the likelihood that something is accidentally dropped into the abyss. It’s not wise to leave things in the abyss, but it’s not cheap to get them out either.
Openings in sensitive equipment, pipes, and other hard to reach areas should be sealed off before small parts are allowed in the vicinity. Retrieving small parts may be impossible, or prohibitively expensive, and can cause long term damage of important equipment.