Roller question/blond moment

Ok, I am in the middle of rollering my GRiSO, right is done without issues. So I am closing up the right and realize that there is a clean spot I cannot account for; as in "am I missing a bit?".
I know it is a picture of the left cylinder but same on the right. Question is, what goes in the left threaded hole? To the right of it is the oil line attachment point but what is the left one for.

OK, age is kicking in but I cannot account for a part that goes there?

FYI, having a blond moment

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Nothing goes in there on either side....I don't know what it can be for on other variants of use though ...

Paulbrice,

As long as nothing goes there no worries. It just looked to clean thus the worries; have sufficient entertainment with installing the rollers to do something "blond" to muck up the whole job.

The Stelvio has a bracket that goes to the frame that mounts using that hole. On Grisos it is redundant.

Pete