S4. Determine the target’s lowest Armour value

Determine what is the lowest Armour value among valid target units in the target detachment. This is the minimum value you need for attack dice to score hits.

Remember that Infantry units that are in cover benefit from a +1 or +2 bonus to their Armour values.
Example 1. Lowest Armour value in the target detachment — hits and misses

You target an Ork target detachment that contains: Gretchin (Armour 3); Gretchin that are in cover in some ruins (effectively Armour 4); Ork Boyz (Armour 4); Battlewagons (Armour 5).

Any die you roll that scores a 3 or more will be hit. Any die you roll that scores a 1 or 2 will be a miss.