For any Multiple Duplex or Multiple Plug outlets must be plugged directly into the mounted electrical receptacles; they cannot be chained or linked together. Your extension cord or power strip needs to be rated for the products to be plugged in and is marked for either indoor or outdoor use.
Extension cords must be plugged directly into wall outlets. They cannot be “daisy chained,” together. Plug extension cords cannot be plugged into surge protectors or other extension cords. Be sure to take your time when selecting the rig extension cord for the equipment you are using since the damage may not be noticeable at first, it is important to know that you have selected the proper extension cord.
By using a device with a two prong plug into a three-prong extension cord the device is not connected in any way to the ground wire in the cord. You can use the device in this application however you CANNOT place a three-prong device into a 2 prong Plug. This will leave the Ground (third prong) exposed and can cause electrocution if touched. It is best practice to match the number of prongs on the device to the correct extension cord.