Infos about full cover
 

"Combat" -> "Modifier Summary" -> "Concealment (?)"
The "(?)" opens the window "Concealment - Barley -1, Partially -2, Substancially -3. Fully - see 'Cover'".

But where do I find the rules for full cover?

Check the core WoD rulebook in the section entitled "Cover" that starts on page 162, with additional details in the subsection "Firing from Concealment" on page 163-4.

:D I see. So its nowhere hidden in HL. Thanx.

HL tries to provide a summary for quick reference during play - nothing more. Since "full cover" means that the character has 100% cover and cannot be targeted, there are no minuses to dice pool. There are special rules for attacks that penetrate the cover (e.g. a shell piercing a vehicle the character is riding in. Those details are summarized under the section on "Cover", hence the entry just pointing the user to read those rules.