When the castle was built, there was no free-standing scaffolding, so wood logs were driven between the stones until the next layer and

another platform could be added; it wasn't until the castle was finished and all the wooden scaffolding was removed that they realized there was

no way, at the time, to repair the holes.



여기서 


it wasn't until the castle was finished and all the wooden scaffolding was removed that they realized there was

no way, at the time, to repair the holes.



이부분에 it wasn't는 왜 들어가는거야? 


나의 지식으로 직역하면

그것은 없었다 그 성이 끝날떄까지 그리고 모든 그 나무he castle was built, there was no free-standing scaffolding, so wood logs were driven between the stones until the next layer and


another platform could be added; it wasn't until the castle was finished and all the wooden scaffolding was removed that they realized there was


no way, at the time, to repair the holes.






여기서 




it wasn't until the castle was finished and all the wooden scaffolding was removed that they realized there was


no way, at the time, to repair the holes.






이부분에 it wasn't는 왜 들어가는거야? 




나의 지식으로 직역하면


그것은 없었다 그 성이 끝날떄까지 그리고 모든 그 나무로 된 비계가 제거될때까지, 그들은 깨달았다 방법이없다는것을, 당시에, 고치기위한 그 구멍들을.


이라고 해석되는데 


it wasn't는 어떤 역할을 하고있고 어떤 문법으로 들어가있는건지 궁금함