they are treated as weapons in the rules: -10 to attack with them but +15 to parry (Defensive trait)

Why do they not add to armour worn? With these rules, they are completey useless against ranged attacks. Even such a thing as the Arbites riot shield.

Yes, the shield is first and foremost used to defend against melee attacks.

However, in my game I intend to include a new move, called Guarded Move. It's a full action, but you only move att your half move, but all ranged attacks coming directly in front of you hits the shield. I will use the rules for the Combat Shield in Rogue Trader, wich gives a +3 armor bonus to the arm it's attached to and to the body, stacking with other armor. It should be relativly simple to do something similar.

For very big shields, it you could use the rules for the Tower Shield in inquisitors handbook, wich is basicly a portable cover, granting either 6 or 8 ap, depending if its wood or steel. Also the Naval shield from IH also can be used as "cover", giving 8 AP. The guard shield gives 6 ap when used as cover.

...

Basicly, allow any shield you rule to be "big enough" to be used as cover, giving 4-8 ap depending on material. Players smart enough to utilise a shield should be rewarded for it.

Also, re-reading ascension, it states the the arbites riot shield gives 4 ap to the arm it used with, aswell as the body.

In Rogue Trader and Deathwatch, you'll also find the Combat Shield, which similarly grants AP to the arm wielding it and the body. The Deathwatch variant is also a Field effect, making it an exceptional tool.

I thought shields counted as cover on front and side of body worn on.

Praesidium Protectiva from Blood of Martyrs grants 8 extra AP vs ranged attacks on successful parry. This makes sense since shields are not an entirely passive defense like armour, failing the parry check represents not getting shield in place fast enough to block the shot.

Unusualsuspect said:

The -10 is to Attack only, not defense....so you still have a +15 to parry

Can someone point out where it says you get a +15 to parry? I'd love to know because two of my PC's are melee heavy and they kick NPC ass like candy will come out of it.

I can't find it, none of my pdf's work with the search function.

Eskilius Quinn said:

The text should be search-able. Where did you get them from?

The defencive weapon trait gives +15 Parry but -10 Attack.
It should be in the core book at the start of the Armory, where all the other weapon qualities are listed.

description of shields states that using a shield to attack is -20. i personally would have that stack with the -10 from the defensive quality.

however, a decent gm could house rule a talent that would offset some of that penalty due to training/techniques

The Inquisitors hand book also has a couple of sheilds that you can take cover behind.

"Sheilds" in Dark Heresy are lumped in the weapon catageory. The basic sheild is just a primitive or archaic sheild, not designed to block bullets and the like. Some sheilds have rules that let you take cover behind them, some don't.

Sorta seems like they came up with better rules for sheilds after the wrote the first ones.....

Guard shields can provide cover for the user
concealing all of their body should they choose. As cover, a
guard shield provides 6 Armour Points.

The shield you're talking about is described as a generic profile, not a hard-fast definition of every shield in existence. It depends entirely on the size, shape, and composition of the shield. For instance, cardboard won't help against a Heavy Bolter, while a hunk of Adamantium blown off the side of a Chimera is going to render you virtually immune to incoming lasguns if you hide behind it. Check through the supplements, there are tonnes of shields with varied effects.