In these drawings the object is "unfolded" to lay flat on a plane so it can be represented in entirety.
Technique of rabattement is very old: the archaic paintings that predate the Antiquity used similar methods to achieve "intellectual realism" (as opposed to "visual realism" of later times) by unfolding the object to represent its hidden sides.
[4] Rabattement was extensively used by stonemasons in the construction drawings, and, together with projection plane, evolved into a method of descriptive geometry.
Descriptive geometry manuals sometimes use the term "rotation" when discussing moving points and lines, reserving rabattement for shapes and planes, but in practice both operations are identical.
[8] The goal of the rabattement operation is to represent the true shape and size of a face of an object[2] (this is impossible to do with orthographic projection if the shape of interest is inclined with respect to all planes of projection[9]).