Is 1 grit point required for each attack or 1 grit point total if making a full round attack?
"Pinning Shot (Ex): At 15th level, the bolt ace can spend 1 grit point while shooting a crossbow and attempt to pin down its target with the bolt. If the crossbow attack hits, it pins the target to a nearby object, to a wall, or to the ground, entangling and staggering the target. While pinned by the bolt, the target cannot move out of its space until it takes a standard action to free itself from the pinning bolt, except by means of teleportation."