Crossbow, Hand: You can draw a hand crossbow back by hand. Loading a hand crossbow is a move action that provokes attacks of opportunity.
You can shoot, but not load, a hand crossbow with one hand at no penalty. You can shoot a hand crossbow with each hand, but you take a penalty on attack rolls as if attacking with two light weapons.
Crossbow, Heavy: You draw a heavy crossbow back by turning a small winch. Loading a heavy crossbow is a full-round action that provokes attacks of opportunity.
Normally, operating a heavy crossbow requires two hands. However, you can shoot, but not load, a heavy crossbow with one hand at a -4 penalty on attack rolls. You can shoot a heavy crossbow with each hand, but you take a penalty on attack rolls as if attacking with two one-handed weapons. This penalty is cumulative with the penalty for one-handed firing.
Crossbow, Light: You draw a light crossbow back by pulling a lever. Loading a light crossbow is a move action that provokes attacks of opportunity.
Normally, operating a light crossbow requires two hands. However, you can shoot, but not load, a light crossbow with one hand at a -2 penalty on attack rolls. You can shoot a light crossbow with each hand, but you take a penalty on attack rolls as if attacking with two light weapons. This penalty is cumulative with the penalty for one-handed firing.