are 27 cars in rotation when the system is operating. They come in two kinds: Single-ended cars serve the Powell–Hyde and Powell–Mason lines. These cars have an open-sided front section, with outward-facing seats flanking the gripman and a collection of levers that actuate the grip and various brakes. The rear half of the car is enclosed, with seats facing inward and entrances at each end and the car has a small platform at the rear. These cars are long and wide and weigh . They have a passenger capacity of 60, 29 of them seated. These cars must be rotated to reverse direction at each end of the line, an operation performed on turntables. Most of these cars were built or rebuilt at Muni's Woods Carpentry Division. Double-ended cars serve the California Street line. These cars are somewhat longer, having open-sided grip sections at both ends and an enclosed section in the middle. These cars are long and wide and weigh . They can hold 68 passengers, 34 of them seated. The California Street line lacks turning capabilities at each end, resulting in the necessity of the double-ended cars. Some of these cars are former O'Farrell, Jones, and Hyde Street cable cars, while some cars were built at Muni's Woods Carpentry Division. There are 28 single-ended cars available for operation on the Powell lines and 12 double-ended cars on the California Street line. Both types of car ride on a pair of four-wheel trucks, to fit the track's narrow gauge. The term California Street car, as in a car running on the California Street line, should not be confused with the term California Car. The latter term applies to all the cable cars currently operating in San Francisco and is a historical term distinguishing this style of car from an earlier style where the open grip section and the enclosed section were separate four-wheel cars (known as the grip car and trailer). The cable cars are occasionally replaced with new or restored cars, with the old cars being moved to storage for later restoration. There are two historic cable cars in storage in the cable car museum: car numbers 19 and 42, which were used on the Sacramento-Clay and O'Farrell, Jones and Hyde Street lines, respectively. Car barn, power house, and museum The cable-car barn is located between Washington and Jackson Streets just uphill of where Mason Street crosses them.