Fan-shaped anti-grenade barrier that blocks incoming thrown explosives while letting fire out — used by both sides.
When Carl tosses a Hob-Lobber at a heavy gun position on the far side of the Reavers' rapidly-deployed defense, it sticks in an anti-grenade One Way shield — the same type the defenders themselves use — and detonates harmlessly in the air over everyone's heads. Carl gives up on grenades and switches to lobbing Troll Smoke Mantles instead.
The cyborgs' semicircle formation includes several of these shields alongside heavy guns, and more of the fan-shaped barriers keep popping up in front of Carl on the roof, frustrating his attempts to see what is happening in the smoke below.
Fan-shaped translucent energy barriers that snap into existence in front of a firing position, stopping thrown ordnance in mid-flight.
Standard battlefield anti-grenade barrier deployed by both the Reaver cyborgs and Carl's defenders.