This file is from Wikimedia Commons and may be used by other projects.
The description on its file description page there is shown below.
Summary
DescriptionContinuator types.png
English: Adapted from (1996). "A Linear-Time Algorithm for Covering Simple Polygons with Similar Rectangles". International Journal of Computational Geometry & Applications06: 79. DOI:10.1142/S021819599600006X..
The 7 maximal continuator types in a hole-free rectilinear polygon. The top 3 are 1-knob continuators. The bottom are (from right to left) 2-knob, 2-knob, 3-knob and 4-knob.
The blue part of the continuator is its "balcony" - its points not covered by any other maximal square.
to share – to copy, distribute and transmit the work
to remix – to adapt the work
Under the following conditions:
attribution – You must give appropriate credit, provide a link to the licence, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible licence as the original.