Since 1882, membership in the Knights of Columbus has been open to men 18 years of age or older who are "practical" (that is, practicing) Catholics in union with the Holy See.
Since that time, the Knights of Columbus has understood "practical catholic" to mean a Catholic who accepts the teaching authority of the Catholic Church on matters of faith and morals, aspires to live in accord with the precepts of the Catholic Church, and is in good standing in the Catholic Church.