To find the value of \( h \) that makes the multiplication sentence \( h \cdot 1 = 646 \) true, we can use the property that any number multiplied by 1 is the number itself.
This means that:
\[ h \cdot 1 = h \]
So, we can rewrite the equation as:
\[ h = 646 \]
Thus, the value of \( h \) that makes the multiplication sentence true is:
\[ \boxed{646} \]