They walked to the back of the church and stood at the door as their guests filed past. (Para. 4)
Meaning: They walked to the back of the church and stood at the door as their guests walked by them in a line.
file: vi. 1) walk one behind the other 一個接一個地走
The students filed into the meeting hall.學生一個個走進會議大廳。
About 10,000 people a day filed past Tian'anmen Square during the celebration period. 在歡慶期間，每天約有一萬人走過天安門廣場。
2) make a written request for a position 提出
I hope you have filed for safety insurance. 我希望你已參加了安全保險。
vt. 1) put away (papers, etc.) in order 歸檔
Please file these tape recordings. 請把這些磁帶錄音歸檔。
2) place an exhibit among the records of a court, public office, or government 向...... 提出（申請等）
They tried to file a request with the authorities. 他們試圖向當局提出請求。