They can be serviceable (or even good) in a pinch: while on vacation last year, the mirror on my film slr got stuck*, an ongoing issue that can be remediated by unscrewing the bottom plate and oiling gears (as I learned from a web tutorial, except my body is an older and more simple model than shown).
I needed a very small phillips head screwdriver, so I bought a set of miniature screwdrivers at ye local dollarstore, and had the camera back in action in <1 hour.
*blocking the viewfinder. I took several more, perfectly good shots using the point-and-shoot method, to ascertain this would not dislodge the stuck mirror.
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