There are several different rule types. Most of them have some flags that might warrant an explanation;
"Invert condition" can be checked to invert the test in question. An example; If you're looking for an mp3 file, and your search results are cluttered with non-relevant hits, you can set up a rule that says; If filename DOES NOT end with ".mp3", flag it as "DON'T DISPLAY". Inverted conditions are marked with an X in the rule list.
The "Active" flag can be checked and unchecked to temporarily enable or disable a rule.
The "Mark only" flag is special, and is likely to be replaced by something more generic, but currently it can be used to mark search results with a different colour to make the matching results stand out from the rest. To achieve that effect, check "Mark only", and select "DON'T DISPLAY" as the target.
Size rules have three similar uses;
If only "minimum size" is given, the rule will trigger a jump to the selected target if the size is less than the value given. This can be used to filter away small files when looking for something large, such as a video clip.
If both "minimum" and "maximum" is defined, the rule will cause a jump if the size is between the two values.
If only "maximum" is given, the filter will jump if the result's size is larger than the given value.
Name rules perform tests on the results' filenames. The "Condition" pulldown should be quite self-explanatory.
The flag rules can be used to filter results based on the hosting servent's flags; "Stable", "Busy "and "Push". For example, if you are behind a firewall and unable to received pushed files, you can add a rule that directs all results with the Push flag set to DON'T DISPLAY.
The jump rule is used to either set a DO or DON'T flag directly, or it can be used to call one of the free filters for subsequent testing.
IP rules filter results based on the servent's IP address. A typical use for this is to ignore certain spammer hosts which return bogus hits. Or one can auto-download results that come from a certain IP address or network which is known to be fast.
The urn:sha1 rules are special, and can't be edited manually. They can only be added via the right-click-menu in the search results window. They are used to match a given file, and flag it for either DON'T DISPLAY (if picked via the "ignore" menu item) or DOWNLOAD (if picked via the "auto-download" item).
State rules can be used to process results that have already been through a number of other tests. A common application for this rule is to automatically download results that haven't been marked as DON'T DISPLAY. See under "Sample rulesets" for a full example.