I bought a case to install my motherboard in, but I'm a little confused
since the case comes with virtually no instructions. It comes with
some plastic spacers and standoffs - do I need both? I have a feeling
I don't need the plastic spacers, but why would it come with them?
Depends on what you mean by spacers, and they'll try to
provide what may cover more than one size with not all parts
being applicable to your use.
Some boards don't just fit perfectly with each corner
directly overtop the mounting studs, they hang over the
studs a fair bit and have a second hole that doesn't match
up with a mounting stud, but can have a plastic standoff put
in to keep it from flexing, particularly if there are ports
near this area where wires or cards might be inserted with
some pressure.
I prefer little rubber feet though, the bumper-type that
comes stamped out of a sheet. I position those at various
places around the board for the same reason, so cards or
cables, etc, don't flex the board... though they have to be
the right height, usually about 7.5mm but not always, less
often so (shorter) on OEM cases. I suppose if the spacers
are the right height (and/or if you can to flush-cut the
studs off of them), you could use them instead of rubber
feet for reinforcement if you had some super-glue or cement
to attach them, though I've never tried this as the rubber
feet with peel-off liner are more convenient, and easier to
remove later.