掲示板 and 掲示: a board, posting, and posted content
Compare physical and electronic 掲示板 with 掲示 in posting a notice or describing posted rules, distinguishing the medium, the action, and the possibility of posting.
掲示板 names a physical or electronic board
「駅の掲示板に地域の催しの案内が貼られていた。」 says that a local event notice was posted on the station bulletin board. 掲示板 names the physical board, and 貼られていた describes the notice being displayed there.
「質問は授業用の電子掲示板にも書き込めます。」 says that questions may also be posted on the class's online message board. 電子掲示板 is an electronic medium. 書き込めます expresses the possibility of posting, rather than a completed post.
掲示 connects to posting and displayed material
「入口に休館日のお知らせを掲示した。」 describes posting a notice of the closed days at the entrance. 掲示した presents the posting action, unlike 掲示板, which names the board itself.
「掲示された規則を読んでから中へ入った。」 says that the posted rules were read before going inside. 掲示された modifies 規則 and identifies the rules that were read. Reading them does not establish compliance with every rule.
Separate the medium from possibility and action
In 電子掲示板にも書き込めます, the board is a medium on which a question can be posted. お知らせを掲示した focuses on the action of posting a notice. The examples distinguish a board from posting and a possibility from a past action.
掲示板 covers the physical and electronic boards in these sentences. 掲示 appears in the act of posting a notice and the description of posted rules. Identify what is being named and what is being done in each sentence.
What roles do 掲示板 and 掲示 have in 電子掲示板にも質問を書き込めます and お知らせを掲示した, and has the question already been posted?
Show the answer and why
掲示板 names the electronic board where a question can be posted, while 掲示 appears in the action of posting a notice. 書き込めます expresses possibility, so it does not say that the question has already been posted. 掲示された規則 connects posting to the displayed rules.