Draw the two pictures such that the two points coincide. It is basically fold. Combine a list of pictures using the indicated sequencing operator. Sequences two lines, drawing the second line so that its start point coincides with the end point of the first line. These operations relate to naming and numbering of pictures.
All pictures come with some of their points named, as described above.
Users may add additional named points using the operations listed here. An irritating subtlety here has to do with numbering of subpictures. On the other hand, some structure is desirable. So, the group operation prevents the flattening of that picture within a larger picture. When named pictures are added using addNamedPic or addNamedPics, they are automatically grouped.