Blessing for the Mitzvah of Ma’qa

Hello Rabbi!
In response to the question of why there are mitzvot that have no blessing upon them, the poskim write that regarding mental mitzvot that did not distinguish us from the Gentiles, one should not say, “which we sanctified with its mitzvot” (the rabbi presented this opinion in the article “General Introduction, and the Fundamentals of the Laws of Charity”).

If so, then why bless the construction of a railing? After all, it is a clear intellectual commandment?

The Chazon Ish, in Likutei Hom, wrote that the mitzvah of a railing is not rational because when a person goes up to the roof, he is more careful and would think that there is no need for a railing, but it is difficult to accept his explanation because a person who does not build a railing is considered in the eyes of the world to be endangering his family members.

A. Why bless a railing?
on. Does the rabbi know of any other mental mitzvot that require blessings?

thanks