Practical example covering common needs

Specific filesystem thresholds

By default you will be alerted if any filesystem runs out of space, regardless the mount point or the driver letter. But maybe you don't care about drive C: and you want to be alerted about drive D: getting full.
Disable the default rule Agent - File system free percent (any disk) .
Go to the host list and select any host that has a drive D: attached. Open the metrics section of that host, navigate to the fill-level of drive D: and click on the wand icon.
Create a rule for a specific disk
Now you can create a rule only for a specific disk identified by a drive letter or a mount point. You can choose wether you create that rule for all hosts or just for the one you used a "starting point" for the rule creation.
Supervise a filesystem by drive letter.