This technique consists of simultaneously heating both the external surface of the pipe and the internal surface of the socket fitting until the material reaches fusion temperature; inspecting the melt pattern; inserting the pipe end into the socket; and holding it in place until the joint cools. Figure 6.4 illustrates a typical socket fusion joint. Mechanical equipment is available and should be used for sizes larger than 2 inches in diameter to attain the increased force required and to assist in alignment.