Think of a door that has simply been left unlocked. Nobody at the door is checking a list, nobody had to be invited, and behind the door there is something worth seeing — a home, a classroom, a house that is for sale. For as long as the door stays open, anyone may walk in, look, and walk out again.
Two branches
家裡的門對人開著
這一支最貼近核心畫面：門開著的就是自己家，走進來的是朋友。差別只在門開多久——一直開著，還是只開一個下午。
noun · B2
If someone keeps open house, or if it is open house at their home, visitors are welcome there at any time, without an invitation and without telling anyone they are coming.
門戶常開；隨時歡迎來訪
把門打開給外人參觀
同一個畫面搬到學校、公司或一間要賣的房子上。走進來的不再是朋友，而是陌生人；他們進來不是為了作客，是為了看清楚裡面。門一樣是開的，一樣不用邀請，時間一到一樣關上。
noun · B1
A day when a school, a company, a university or another organization opens its doors to the public, so that visitors can walk around, look at the work done there, and talk to the people who do it.
開放參觀日