Heres what some of my light reading dives into on blessing:
"Anytime a preist or deacon blesses a religious article, such as a rosary, statue, or medal of one of the saitns, he makes the sign of the cross with his right hand over the objects and sprinkles holy water on it after saying the prayers of blessing. The holy water reminds the owner that the blessed item is now reserved for holy use (to enhance prayer life, for example) and shouldnt be used for profane (nonreligious) use.
So almost anything can be blessed, as long as the item will only be used for moral purposes and isnt foing to be sold. Blessings arent magical, but blessings do change an object into a sacramental, which means that its a reminder of God's grace and generosity and, particularly when used in conjunction with prayer, invokes God's blessings on all who use it"
- Catholicism for Dummies