fields (again)

http://imgur.com/QbThc0g
Okay plots below labelled could be placed on forest floor as long as ONLY ONE SIDE WAS TILED.
When cursor is on block labelled A there is no message, no option to build etc.. just nothing
When cursor is on block labelled B told cant build there.
Tried with and without paving in place.
I understand B cos of dug dirt, but why not A?
(ps how do you post the actual bloody image? Im a techie idiot, words of one syllable please)
Okay plots below labelled could be placed on forest floor as long as ONLY ONE SIDE WAS TILED.
When cursor is on block labelled A there is no message, no option to build etc.. just nothing
When cursor is on block labelled B told cant build there.
Tried with and without paving in place.
I understand B cos of dug dirt, but why not A?
(ps how do you post the actual bloody image? Im a techie idiot, words of one syllable please)