This phrase suggests a number of ideas about the wall it describes. The little family takes walks now but does not admire the flowers they once did, as all of the homes in their neighborhood are being surrounded by walls designed to keep out intruders. The couple examines the various structures and decides that there is only the one which is
worth considering. It was the ugliest but the most honest in its suggestion of the pure concentration-camp style....
In other words, the wall looks brutal, and its effect on any human body would be absolutely brutal. It is topped with barbed wire with "serrated" and "jagged blades" so that there is simply no way that a person could climb the wall and not be ensnared by its horrible "fangs." The more a person would struggle against the wire, the more horrible their injuries would be. Just as the camps were surrounded by such horrific bounds, so are the homes that have the "Dragon's Teeth" security wall.
Another suggestion, however, is that the walls do not simply keep people out, but also imprison people within. Barbed wire fences around camps were meant to keep Jewish prisoners from escaping. To surround one's home with such a wall, one that calls to mind concentration camps, is to effectively imprison oneself and restrict one's own freedom.