Sometimes no matter how hard you try something gets lost in a hard-to-reach area. When this happens you can grab a fishing pole, a good hook, and hope for the best, or… You can prepare ahead of time by equipping yourself with a number of these retrieval tools and kits.
Each has their own benefits, but the important thing is to anticipate what you may be retrieving. You will need a way to find items, assistance in seeing them clearly, and a way to safely remove the items without damaging the surrounding equipment. Usually this means having a borescope or inspection mirror to find the objects, a flashlight for proper lighting, and some form of grabber to get a grip on the item and pull it from its temporary resting place.