Here is the sign for plug or outlet. Hold up your index finger on your non-dominant hand vertically, while the rest of the fingers are in a fist. Then take your dominant hand, make the ASL letter sign for 'V', and horizontally fork the index of your other hand with the "prongs" of your 'V' hand. It's like you're plugging into a wall outlet.
Teach this sign to your baby or toddler, but along with a clear warning not to touch the plug. Better yet, have outlet covers in place for all exposed outlets throughout your house!
We mainly use this sign as a safety warning. Please note that children under three years of age should not plug or unplug electrical appliances.