Like the nail attack, the nail attack strum has many different ways of being notated. Common ways include:

In some countries, this technique is referred to as the "Attack Mute", or "AM". If you see that instead of "NA", it most likely means this same nail attack technique.

If you're here because the nail attack strum is marked as 'easy' compared to the nail attack's 'hard' difficulty, stop and learn the required nail attack first. This technique is only easy to learn if you can do the nail attack.

Once your nail attack has achieved the percussive sound consistently, you can pair it with a downward strum. In the basic nail attack technique, your fingers bounce back towards the palm of your hand after the nail attack and your wrist only moves towards and away from the strings.

By adding the strum to the technique, your fingers no longer bounce back and instead extend further. Your wrist can move up and down like you would in a normal strum too.

This strum is very fast as you'll be doing the flicking motion of the nail attack as you strum downwards. Your arm can move up and down to assist with the strum. You only need to extend your fingers enough so that they strum all the intended strings. You should still hear the nail attack sound while doing this motion.