I have a question about the grammar behind saying what seems like a simple thing, but is proving to be hard for me. "The door is locked." In English it's an expression of state using an adjective.
However, research on 鎖 has not been very fruitful as it is apparently just a noun (actually it can act as a verb, my bad). The most consistent examples of "the door is locked" I have been able to understand from Jukuu have indicated this structure:
First, is this correct? If so, what is the grammatical breakdown? I haven't run across a structure like this before, it doesn't fit a result complement or any other complement structure I know.
It seems like 上 is the verb. Is this the same sense as its use in 上廁所？ I'm also confused by the 了。Is it indicating change? Completion?