Sometimes, the negative modifiers applied to a roll To Hit may result in you needing to roll a 7 or more on a single D6. For example, a model with BS2 normally hits on a roll of 5 or above. But if you apply a -2 modifier to a roll of 5 it becomes a roll of 3. Therefore, you would need to roll a 7 to achieve the target number of 5+, which is not, strictly speaking, possible on a six-sided dice.

In such cases, there is still a chance of hitting. Roll To Hit as normal. Each dice that rolls a natural 6 represents that chance of hitting and is rolled again, as shown below:

To continue the previous example, if a unit of models with BS2 suffered a -2 To Hit modifier, simply roll To Hit as normal. Then, take each dice that rolls a natural 6 and roll it again. Each of these dice that rolls a 4 or more is a hit.