Pinning
(Rule)Description: If a unit other than a vehicle suffers any unsaved wounds from a pinning weapon, it must immediately take a Pinning test. This is a normal Leadership test. If the unit fails the test, it is immediately forced to go to ground. As the unit has already taken its saves, going to ground does not protect it against the fire of the pinning weapon that caused the test (or indeed of any other weapon fired by the same unit that phase)
As long as the tests are passed, a unit may be called upon to take multiple Pinning tests in a single turn, but if a unit has already gone to ground, no further Pinning tests are taken.
If the special rules of a unit specify that the unit can never be pinned, the unit always automatically passes Pinning tests. Such units can still choose to go to ground voluntarily.