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 一个接一个地走
The students filed into the meeting hall.学生一个个走进会议大厅。
About 10,000 people a day filed past Tian'anmen Square during the celebration period. 在欢庆期间，每天约有一万人走过天安门广场。
2) make a written request for a position 提出
I hope you have filed for safety insurance. 我希望你已参加了安全保险。
vt. 1) put away (papers, etc.) in order 归档
Please file these tape recordings. 请把这些磁带录音归档。
2) place an exhibit among the records of a court, public office, or government 向...... 提出（申请等）
They tried to file a request with the authorities. 他们试图向当局提出请求。