Hey guys,
I’ve noticed on 3 separate occasions we’ve had PCs wanting to threaten someone, such as T’aria with a dagger at someone’s throat, and Sunedilar with his spiked chain; I think it’s an effect of having an all-evil group

As far as I can tell, there’s nothing in the rules that allows for the kind of automatic hit that these maneuvers should have; instead, the only way to do it is to “ready”, and then hope you make your attack roll. So, I made up a rule to handle this, detailed below. If anyone doesn’t like it, they are always free to just use the normal ready maneuver and an attack roll will decide if you hit or not. And if anyone knows a similar rule in another D20 source, let me know and I’ll probably use that instead. Anyway, here’s the rule:
Covering attack:
As a special “ready” action, a character may attempt to cover a target with a weapon. For this to work, the attack must be non-bludgeoning, and if ranged, be within 30 feet. The character making a covering attack makes his attack roll immediately, taking a –4 penalty. The penalty is due to the difficulty in positioning a weapon to guarantee a hit. This penalty is only –2 against targets who have lost their Dex-based Armor Class, such as those who are flat-footed, grappled, the target of a feint, etc. If this attack roll succeeds, the attacker is then “readying” the damage, meaning that he defines what actions will trigger his attack, with the attack automatically hitting if the action occurs. At that point, damage is rolled normally. If the attack roll failed, then the attacker failed to cover his target this round.
As with any ready action, you can’t respond to any actions that you can’t perceive, so hidden or invisible actions may disrupt your covering attack, and you can stay “ready” indefinitely, but you must lose the readied action to perform any other action. At any time that your initiative comes up again, you can either re-ready the damage, or just cause the damage then without the triggering action taking place.
Be sure if you use this rule that it’s very clear you’re not just readying an attack. For example, if you say “The character shoots him with his crossbow if the target moves”, I’ll assume that’s a normal readied attack. If you word it as “The character tries to cover him with his crossbow, then shooting him if he moves”, I’ll know you’re using the covering attack, and I’ll preroll the attack roll with the appropriate penalty.