Supressing Fire
(Rule)Description: f a non-vehicle model suffers one or more hits from a shooting attack made by this model, the target must take a Leadership test once this model has finished its attacks for that phase. This is called a Pinning test.
If the target fails the test, it must immediately Go to Ground (see Warhammer 40,000: The Rules ). As the target has already taken its saves, Going to Ground does not protect it against the fire of the weapon that caused the test - it's too late! As long as the test is passed, a target can be called upon to take multiple Pinning tests in a single turn, but only once for each model shooting at them. If a model has already Gone to Ground, no further Pinning tests are taken.
If the special rules of a model specify that they can never be Pinned, they automatically pass this test. Such models can still Go to Ground voluntarily if they wish.