Detecting adjacent parts/bricks?

Could you give more information on your current problem? Because best solution depends on the situation, sometimes you might want to use raycasting, other time touched event would work better.

I'll second that. You could raycast, but it could be comparatively expensive compared to what might be wanted.

I'm intending on creating a sort of fog of war for an RTS I've been working on, it's sort of a risk-type RTS (map based).

Then it sounds like you should learn how to use raycasting. There is no real definitive answer or code I can give you, but check out how rays work: http://wiki.roblox.com/index.php?title=Raycasting

Thanks for the tip

http://wiki.roblox.com/index.php?title=API:Class/BasePart/GetTouchingParts This may help somewhat, if you don't have to be exact.

FindPartsInRegion3 is more likely to be helpful than raycasting for some kinds of fog-of-war

I believe you could create a table and go game.Workspace:GetChildren() inserting them into a table then finding the magnitude of all parts within the workspace and then do something if a part has a magnitude of 2 or 3 whatever you want it to be