Seam goes down, as oriented to the motherboard. If the slots are vertical, usually to the right? If you have a rare, weird machine, just remember which way it goes. FFS, there are 2 choices.
EDIT: Having said all that, not sure I've seen a machine that orients the seam to the left. ?
It kinda is keyed. Seam goes down.
But does it go right or left, back or forward in other rotations?
Seam goes down, as oriented to the motherboard. If the slots are vertical, usually to the right? If you have a rare, weird machine, just remember which way it goes. FFS, there are 2 choices.
EDIT: Having said all that, not sure I've seen a machine that orients the seam to the left. ?
Until they created upside down Jacks
That's true - I mean to make the keying more obvious. As it stands it's all internal and difficult to see.