Part of a set of components which may be assembled in all sorts of ways to create a wide variety of stone buildings ranging from simple farmhouses through posher urban terraces to more complex villas, hotels and even palatial manors, but without putting undue strain on system resources because the same basic units may be used again and again in various combinations.
A smaller dormer unit of a slightly different pattern, preset at a notional height ready for use with the main units. Once again it is doubled so that it can be rotated through 180 degrees to present a different face.