A wedge, a lever, and a wheel and axle are types of simple machines, but a block and tackle is a complex machine because it is a combination of simple machines. A block and tackle is made from a rope or cable threaded between two or more pulleys.
There are six simple machines. In addition to the three listed above, the pulley, the screw and the inclined plane are all simple machines. Because at least two pulleys are generally involved, the block and tackle qualifies as a complex machine.The pulleys along with the rope or cable are used to lift heavy items. This type of machine is frequently used on boats. On a sailboat, for instance, it allows easier management of the mainsail by one person.