  Active galactic Nuclei (AGNs) with their relativistic jets pointed towards
the observer, form a subclass of luminous gamma-ray sources commonly known as
blazars. The study of blazars is essential to improve our understanding on the
AGNs emission mechanisms and evolution, as well as to map the extragalactic
background light. To do so, however, one needs to correctly classify and
measure a redshift for a large sample of these sources. The Third {\it
Fermi}--LAT Catalog of High-Energy Sources (3FHL) contains $\approx1160$
blazars reported at energies greater than $10$\,GeV. However $\sim$25\% of
these sources are unclassified and $\sim$50\% lack of redshift information. To
increase the spectral completeness of the 3FHL catalog, we are working on an
optical spectroscopic follow up campaign using 4--m and 8--m telescopes. In
this paper, we present the results of the second part of this campaign, where
we observed 23 blazars using the 4\,$m$ telescope at CTIO in Chile. We report
all the 23 sources to be classified as BL Lacs, a confirmed redshift
measurement for 3 sources, a redshift lower limit for 2 sources and a tentative
redshift measurement for 3 sources.
