Then along the hidden way they went in single file.

The three friends could only go in single file on the cramped path.

The tracks, made by goats, forced the Companies to go in single file.

They went in single file along the steel catwalk with the child leading.

We went in single file over the rise and down its other side.

The alleyway was so narrow they had to go in single file.

They found the path and went along it quietly in single file.

We went in single file, no more laughing, very little talk.

We turned to the left, going along in single file, the surf close beside us.

The narrowness of the path means that we must go in single file.