Mechanics of "On Striking"

Evening,

I just wonder how On Striking works. Does it trigger when you swing vs an enemy, do you have to hit and pass block etc ?

I have tried to search a little on this, but have found more then 1 answer

So whats the deal? (Its brand bow, attacking melee..)

Regards

/Heffaklump|||Have a look at the skill granting items link in my sign, think it should be useful.|||Thx for the info. So that means if my enemy blocks with shield, i wont get no bonespears flying ?

/Heffaklump