Source: Warhammer Fantasy: 8th Edition

Flank and Rear (Multiple Close Combats)
URL Copied!

Bonuses for flank and rear attacks can only be earned once per unit attacked in the flank or rear – having multiple units attacking the same unit does not grant additional bonuses.

If two units of Dwarfs are attacking a single unit of Orcs in the same, or both, flanks, then they would only receive +1 Combat Result.
If one unit of Dwarfs is attacking the rear and the other is attacking the flank, they would receive a combined Combat Result bonus of +3 (+1 for the flank and +2 for the rear).
If the two units of Dwarfs are attacking two different units of Orcs in the flank, and those Orcs were all part of the same multiple combat, then the Dwarfs would score +2 Combat Result (+1 for each flank attack).

Previous - Extra Ranks (Multiple Close Combats)

Next - Charging (Multiple Close Combats)