XYZ

The cross the fork the zigzag—a few straight lines
For pain, quandary and evasion, the last of signs.
—Robert Pinsky

O.K., I get that X is the cross (pain), Y is the fork (quandary) and Z is the zigzag (evasion). What does the author mean by "the last of signs?" Such short lines and they are giving me a headache!