It hit me like a brick wall

The speaker was talking about how difficult a final exam was.  Given the context, this is a mash up of “hit me like a ton of bricks” (to surprise or shock someone) and “hit a wall” (coming up against an insurmountable obstacle).  The exam must have been difficult and a surprise!  The confusion is obvious: both expressions contain the word “hit” and certainly walls can be made of bricks.  The expression “hit a wall” is also sometimes stated “hit a brick wall”, making the two expressions have even more commonality.  Perhaps the speaker is a Pink Floyd fan as well.  A big thanks to Adam Jacob for hearing this one and passing it on.