Lock-up, Avoca, forms part of a complex including a court house, police magazine and residence. The lock-up was constructed in 1867, presumably to the designs of the public works department if Victoria. Built in coursed bluestone with a gabled slate roof, the symmetrical structure has a gabled porch. Features are the plinth, sills and iron-grilled doorway, vents and corner detailing. The lock-up forms part of a complex of buildings important in the early history and townscape of Avoca. The lock-up is a representative example of a modest bluestone lock-up of the period. Architecturally, the structure is notable for its masonry work and its detailing, which is restrained and is typical of classically derived, vernacular designs by the Public Works Department during the period. Lock-up, Avoca, is in good condition and intact.