The common purpose of the Ninth and Tenth amendments is to limit the power of the federal government by protecting rights not listed in the Constitution to give them to the people.
The Ninth Amendment (1791) protects the individual's right and limits the central government, stating that the rights addressed weren't final and didn't deny or disparage the existence of other rights not listed, retained by the people.
The Tenth Amendment (1791) grants the powers that the Constitution neither delegated to the federal government nor prohibited to the states, to the states and the people. It allows states to establish their own laws as long as they aren't contrary to the federal government's laws.