Like other hunters, including Bobby and John, Mary Winchester has a storage unit in which she keeps weapons, mystical artifacts, and dangerous items. It is located in unit seven of an UL-2MAT Storage facility just outside of Grand Rapids, Minnesota. The combination to the lock on the door is Dean's birthday, 1-24-79.
It has a booby trap like John's Lock-up was seen to have in 3.03 Bad Day at Black Rock, with a shotgun connected to a trip wire.
Some of the items that can be seen in the warded lockers include a severed head in a jar, a doll, and an Enochian puzzle box that contained the demon Abraxas. After the events of 14.11 Damaged Goods, it also has a broken devil's trap on the floor near the lockers.
After being kidnapped by Nick, Mary leads him to her lock-up where the Enochian puzzle box containing the demon Abraxas is located. After avoiding a shotgun booby-trap, Nick breaks into the warded lockers in the lock-up until he locates the puzzle box. Kidnapping the facility's security guard Jeff, Nick places him within a devil's trap in the lock-up and releases Abraxas before being confronted by Sam, Dean, and Sheriff Donna Hanscum, who'd tracked Nick through his stolen van. After a confrontation, Abraxas is killed by Nick with an angel blade and Nick is subdued and arrested for his murder spree.