This came up in my last game. What are the actual rules for drawing line of sight? Can I shoot at a bad guy from behind another character? I thought this was represented by the -4 for firing into melee, but the DM said (with some uncertainy, because he wasn't sure) that the character blocked line of sight. I flipped through the PHB and the SRD looking for the exact rules on drawing line of sight, but couldn't find what I was looking for.