Learn English Online - Idiomatic Expressions
Definition of Idiomatic Expressions

What does set a thief to catch a thief mean?
Meaning of idioms with examples...
set a thief to catch a thief
The best person to catch a thief is another thief, because he or she knows how thieves think.Example(s):
The government set a thief to catch a thief. They hired a hacker to entrap other hackers who tried to break into the Pentagon's databases.
This idiom is in the crime category