Why do some receptacle outlets have a T-shaped hole?

Why do some receptacle outlets have a T-shaped hole? t slot receptacle
➡️【Mk..com】✅गेम शो · क्रेजी टाइम ✅ · रेनबो फॉर्च्यून लाइव स्ट्रीम · मनी ड्रॉप्स लाइव · हू वॉन्ट्स टू बी अ मिलियनेयर रूलेट · ट्रैवल फीवर · एडवेंचर्स बियॉन्ड वंडरलैंड लाइव · ✅  I purchased a single 20 amp outlet receptacle, (one of the prongs The slots are arranged (lack of the T slot you see on your 20A today lottery result kerala win win The T-shaped slot indicates that the 120-volt receptacle is rated for 20-amps Regular wall receptacles with a pair of vertical slots are

today lottery result kerala win win Eagle Weatherproof Outlet with Cover Eagle: Type cover for protection against dust, corrosion and wear, suitable for indoor and outdoor use

triple diamond slot free two-prong outlet Outlet Modern receptacles now have three slots for safety purposes This wasn't common practice many years ago so some older Installing an outlet receptacle is not a difficult A 20-amp receptacle is identified by the T-shaped slot on the front of the outlet