Orientation

Reading the ground pin before you order

This is the thing worth checking with your own eyes. A plate cut for one direction will not sit right on the other, and what separates them is a single round hole.

About 430 words4 sections

What you are looking at

Each half of a duplex receptacle has two flat slots and one round hole. The round hole takes the ground pin, and everything about orientation comes down to where that hole sits.

Round hole below the flat slots: ground pin down. Most outlets in American homes are hung this way.
Round hole above the flat slots: ground pin up. Common in remodeled rooms, kitchens, offices and newer construction.
Slots running sideways: the receptacle is rotated, and no concealer fits it.

Why both directions exist

Nothing requires one direction over the other, so both are correct and both are common. Electricians have their own habits, and a room rewired years after the house was built often ends up the opposite way round from the rest of it.

Some installers point the ground pin up on purpose, reasoning that if a metal faceplate ever worked loose and slid down across a plug, it would land on the round ground pin before it reached the two flat blades. Others do it to mark a receptacle that a wall switch controls. Either way you cannot work it out from the age of the house, which is why looking is faster than reasoning.

Why a plate for one will not do for the other

The prongs are fixed in the body, and the body is built around them. On the wrong orientation the cord would leave at the bottom instead of the top, the face would hang off the outlet rather than over it, and the part meant to cover the spare receptacle would be up in the air above it.

Turning the plate over does not solve it either, because then the printed face is upside down and the cord channel points the wrong way. So we cut two separate pieces and the difference between them is real, not a label.

Checking it in ten seconds

Stand in front of the outlet the piece will actually go on. Not another one in the same room, because they do not always match.
Look at the upper set of openings, since that is the set our prongs use.
Find the round hole. Below the slots means ground pin down. Above them means ground pin up.
If furniture is in the way, take a photo with the flash on rather than guessing from memory.

What you see	What it is called	What fits it
Round hole under the slots	Ground pin down	Our standard plates
Round hole over the slots	Ground pin up	Our inverted plates
Slots lying side by side	Rotated receptacle	No concealer fits