BlockingVolume
A Blocking Volume is a Brush that only provides collision. It replaces UT's Invisible Collision Hull, which was prone to semisolid errors.
It's basically an invisible brush that is there for the only purpose of blocking actors from moving into a space. These can be used for complex objects where you may want to make them nonsolid, but still block movement (for map efficiency reasons), or if there's a space that a player could become trapped in so you do what's best for them and keep them out of it (unless you decide to make said space a killzone, always good for a couple laughs 
).
By default classblocking is disabled, and the blocking volume will block players, but not projectiles.
Relevant Properties
- bClassBlocker
- This makes the BlockingVolume block classes from the array, and ONLY these classes. If this property is true, the Collision settings have no effect.
Collision
The settings for what the BV blocks are under Actor/Collision.
Related Topics
Discussion
Highlander: Re:Blocking Projectiles. Try setting bBlockZeroExtendTraces or bBlockNonZeroExtentTraces to true or fiddle with the settings under collision. (Not at home system so cant check)
Radiosity: It's bBlockZeroExtentTraces to block projectiles bBlockNonZeroExtentTraces is used for players and bots and is true by default in a blocking volume.
King Mango Class blocker is not exactly that simple. I tried using a class blocker for vehicles. No matter what class I entered they still fell through. I tried ONSHoverTank, ONSPRV, ONSVehicle etc... Had to set bBlockZeroExtentTraces to true before it would block vehicles.
But the real reason I'm here is to find out if anyone has sussed how to block a player only? Shock secondary is a NonZeroExtent trace so a BV will block those if it is set to block players. Also, I tried to set UnrealPlayer and xPlayer to class but also these will not block unless the correct extent setting is chosen. Seems kind of pointless to have a class blocker? I think it's broken.
Wormbo: UnrealPlayer and xPlayer are Controller classes, what you want to block are Pawns, e.g. xPawn. Note that the guided RedeemerWarhead and Vehicles are Pawns as well.
Aero: See here... I have sheets that are BlockingVolume (UT2004), but they dont block anything. Is it because I need cubes for them? Or is it because the sheets are not solid (If so how do I make them solid?)? Someone, help meh. 
zugy: Sheets act as non-solids regardless of the type you set them to...use cubes...
