A parcel locker is a lockable unit where mail carriers can leave larger items that won’t fit in a standard mailbox. They are designed to keep parcels safe from theft and unsavory weather. Parcel lockers are often attached to Cluster Box Mailboxes (CBUs), either alongside them and/or with them. When a mail carrier is unable to fit a package into a standard mailbox slot, they will place the package in a parcel locker. This provides a more convenient and secure delivery option, avoiding leaving large parcels out in the open. Customers are given keys or codes for newer keyless models that will allow access to their package. The USPS developed the gopost® parcel delivery locker concept to offer customers an easy, convenient, and secure delivery option. The parcel delivery locker pilot was implemented in February 2012, providing customers with a free alternative to use 24 hours a day for parcel shipment and receipt. Anyone can purchase parcel lockers, and there are privately owned parcel lockers as well as those owned by postal services.