The word "blockhouses" refers to fortifications, often made of timber or stone, that were built to protect settlements or military positions. Antonyms for this term could include "vulnerability," "exposure," or "openness." These terms convey a sense of being unprotected or at risk of attack, rather than fortified and secure. Additional antonyms might include "demolition," "disrepair," or "dilapidation," which imply that the structures are no longer functional or have fallen into a state of disuse. Altogether, the antonyms for "blockhouses" suggest a lack of protection or stability, and highlight the importance of defensive structures in times of conflict or uncertainty.