Abstract: Locking devices and methods of using the devices for interlocking two, three, four or more electrical type extension cords together with each other and/or with electrical cords on appliances and tools, to one another. Versions of the devices can include side facing slots having various configurations that allow portions of the electrical cords to be wrapped around and snappably held within. Pulling the cords apart can tighten the cords into the slots. The devices can have various configurations such as being ruler shaped, fan shaped ends, fork shaped ends, and the like. Coils and springs can be located on the ends of the devices in place of the slots to also allow for the cords to be locked. Indicia ruler markings can be provided on the device so that it can be used as a measuring tool.