Apparently, I install the washers on my safety eyes upside-down. The bump is supposed to face away from the eye, according to every site where I found instructions. I’m going to guess they’re easier to put on that way. The little spikes I stab my fingers with are supposed to grip the fabric and stabilize the eye.
I have no intention of changing, though. I place them bump down for a reason: on the eye sizes I use, the washers are always far larger than the eyes. My amigurumi are small, and there’s generally a strong curve around the eye. Putting the washers on “correctly” can create ridges around the eye; putting them on bump down gives a bit of clearance above the washer.
I haven’t been able to find any information about the security of the washers in either orientation, and I’m not equipped to measure it myself, but they certainly don’t come off easily even when upside-down.
This is the sort of thing I research on a Sunday night.