The cord connects with the socket at _P_, and the current turned on. It is attached with the iron by a piece _R_, made of non-conducting and heat-resisting material and arranged to make contact with the heater terminals by two brass plugs that are insulated from the body of the iron and afford easy means of making electric contact. The contact plugs are shown in Fig. 227. To make electric connection, the contact piece is simply pushed over the plugs, where it is held in place by friction. Instructions which accompany a flat-iron when purchased advise that the attachment piece be used in turning off the current. The reason for this is because of the flash that accompanies the break in the circuit when disconnection is made in the socket. This flash is really a small electric arc, that forms as the circuit is broken and which burns away the switch at the point of disconnection. The arc so formed burns away the contact pieces in the switch and it is soon destroyed. The attachment piece will stand this wear more readily than the socket switch and hence is preferable for disconnecting. The irons are frequently provided with a special switch for the service required in the flat-iron. [Illustration: FIG. 227.--Electric flat-iron showing position of the heating element and contact plugs.] A spiral spring connected to the attachment cord prevents it from kinking when in use and thus breaking the conducting wires. The attachment cord is made of stranded wires to make it flexible. The strands of fine copper wire are made to correspond to the gage numbers by which the various sizes of wire are designated. In use the constant movement of the iron tends to kink the cord and thus breaks the strands. This action is most pronounced at the point where the cord attaches to the iron. For this reason a spiral spring wire encloses the cord for a short distance above the attachment piece. After long usage the cord is apt to break in this vicinity. It may usually be repaired by cutting off the ends of the cords and new connections made in the attachment piece. When the iron is in use the slack portion of the cord is kept from interfering with the work by the coiled wire _S_, which connects with the cord at any convenient place. Electric flat-irons are made in a variety of styles and forms, the mechanism of each possessing some particular advantage, but all are provided with the same essential parts, chief of which is the heater with its electric attachment piece. In Fig. 228 is shown very clearly the construction of an example in which attention is called to the points of excellence that are required in a particularly serviceable iron. The form of the heating element which is recognized in the iron is also shown in Fig. 228. [Illustration: FIG. 228.--Electric flat-iron heating element.]