A Dominican apostolate, the confraternity is open to all Catholics (including married Catholics) who want to commit themselves to a chaste/pure life. It was founded in the 17th century and is based on an incident in the life of St. Thomas Aquinas.
Thomas’ family opposed his desire for the monastic life so his brothers kidnapped him and locked him in the family’s tower. They then hired a prostitute to seduce him hoping it would cure him of his wish to live as a chaste monk. Thomas’ flew into a rage, grabbing a red-hot iron poker from the fireplace he chased her out of the room. He then emblazoned a cross on the door, fell to the floor, and thanked God.
He then had a vision of two angels who girded his waist with a cord and said, “On God’s behalf, we gird you with the girdle of chastity, a girdle which no attack will ever destroy.”
For a nominal fee you can order the enrollment packet here; it includes a pewter medal on a chain and a cord to be worn around the waist. It also includes prayer cards, brochures, and a booklet. It’s only $8.50. The medal and cord are consecrated during the lengthy rite which initiates one into the confraternity. You have to find a Dominican priest whose willing to perform the rite.
Even if one doesn’t join, saying the prayers on a daily basis or when you are being tempted with impure thoughts is a powerful way to gain graces to resist.
Their website can be found here