Each shield has a different DC to successfully block an arrow, representing the difference between shields with which it is very easy to block (tower shield) and those with which it is nigh impossible to block (buckler). Any condition that would make you lose your shield bonus to AC makes blocking a projectile in this manner impossible. | Each shield has a different DC to successfully block an arrow, representing the difference between shields with which it is very easy to block (tower shield) and those with which it is nigh impossible to block (buckler). Any condition that would make you lose your shield bonus to AC makes blocking a projectile in this manner impossible. |