Didn't want anyone to miss this:
Here's one classic example...
Wow! What a rabbit hole of a conversation thread.
I think an appropriate response to the original questions regarding the "classic example" that coach refers to should have been:
When trying to solve this vignette only on the second floor you may neglect information that is on the first floor. In this example there is a door on the ground floor layer that swings out into the lower left hand corner--which is a logical spot for a landing. (It would have been helpful to include a picture of this ground floor layer to illustrate that point)
Since the solution tried to solve the vignette solely on the second floor layer, this door swing was not visible and a railing was drawn against the wall where there actually is a door thus blocking egress, which is a major mistake.
Hope that sheds light to the cryptic and quite small picture provided by coach.
Side notes:
The railing that blocks the door does not have to be continuous along the wall as shown in the "classic example". In fact, this solution is very easily solved by only drawing on the second floor layer--as long as one checks between layers, which I'm sure everyone does with zeal and paranoia at the time of the test.
However, as others have pointed out, you may not get a vignette that you can solve entirely on the second floor layer--better put, you most likley won't get a vignette as easy as NCARB 4.0's practice vignette for the BDCS Stair Design on your actual exam. A stair will most likely wrap under itself or need to use the cut stair tool. Don't be stubborn or optimistic, learn how to use it. It's easy. Go here to find out how:
https://www.youtube.com/watch?v=sf1LWjrMZUgLastly, I'm sure those who didn't know how to wield hammers and preferred using rocks for construction thought hammers sucked too.