Divide each puzzle into 9 regions consisting of exactly 4 squares. There are no intersections where 4 of these regions meet, and dots are located at all the intersections where exactly 3 regions meet. The first puzzle is solved as an example.

1. | 2. | 3. | 4. |

5. | 6. | 7. | 8. |

9. | 10. | 11. | 12. |

13. | 14. | 15. | 16. |

17. | 18. | 19. | 20. |

The solutions are here.