Sometimes known as bike library systems, these bicycles may be lent free of charge, for a refundable deposit, or for a small fee. A bicycle is checked out to one person who will typically keep it for several months, and is encouraged or obliged to lock it between uses. A disadvantage is a lower usage frequency, around three uses per day on average as compared to 2 to 15 uses per day typically experienced with other bike-sharing schemes. Advantages of long-term use include rider familiarity with the bicycle, and constant, instant readiness.