3e SRD:Crossbow, Light
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A light crossbow requires two hands to use, regardless of the user's size. Loading a light crossbow is a move-equivalent action that provokes attacks of opportunity.
A Small or larger character can shoot, but not load, a light crossbow with one hand at a -4 penalty. A Small or larger character can shoot a light crossbow with each hand as noted for heavy crossbows, above.