Casing roller:

A tool composed of a mandrel on which are mounted several heavy-duty rollers with eccentric roll surfaces.

It is used to restore buckled, collapsed, or dented casing in a well to normal diameter and roundness.

Made up on tubing or drill pipe and run into the well to the depth of the deformed casing, the tool is rotated slowly, allowing the rollers to contact all sides of the casing and restore it to roughly its original condition.