The biggest sidewalk sale in town will return to Coolidge Corner on July 28 and 29. The final weekend of the month will also feature a walking tour of the Arcade Building, at 314 Harvard St. Preservation staff will lead the tour of the 1927 building, built by J.J. Johnson and designed by architect George Nelson Jacobs. One of the only buildings of its kind, the Tudor-style, two-story commercial building, with Gothic-style details and skylights, prefigures the modern mall. The tour is at 2 p.m. July 28 Reservations are required, and can be arranged by visiting www.brooklinema.gov/walking. July 28 is also one of the Sundays when the Public Library of Brookline’s Coolidge Corner Branch will be open this summer.