To multiply fractions, we multiply the numerators together and the denominators together:
\[-\dfrac{5}{7} \times \dfrac{1}{5} = -\dfrac{5 \times 1}{7 \times 5}\]Simplifying the numerator and denominator separately, we find:
\[-\dfrac{5}{7} \times \dfrac{1}{5} = -\dfrac{5}{35}\]Since the numerator and denominator have a common factor of 5, we can simplify further:
\[-\dfrac{5}{7} \times \dfrac{1}{5} = -\dfrac{1}{7}\]Therefore, \[-\dfrac{5}{7} \times \dfrac{1}{5} = -\dfrac{1}{7}.\]