Square
Straight sides, a flat free edge, corners left sharp.
Suits: Long nail beds, and anyone who types all day and wants nothing catching.
Watch for: The corners are the weak point. On natural nails they catch and tear before the rest of the nail is ready to be cut back.
Squoval
Square sides with the corners rounded off.
Suits: Almost everyone. It is the shape most people mean when they ask for square.
Watch for: The compromise shape: it keeps the flat edge and loses the corner that snaps.
Round
Sides follow the finger, the free edge is a continuous curve.
Suits: Short nails, wide nail beds, and hands that work.
Watch for: The most durable of the natural shapes, because there is no corner anywhere to catch.
Oval
An egg curve, a little longer than round, sides filed in slightly.
Suits: Shorter fingers. The narrowing does the same job as a pointed toe on a shoe.
Watch for: Filing the sides in takes width off the nail bed, so it is not the shape for nails that are already narrow.
Almond
Tapered sides rising to a soft point.
Suits: The shape most asked for on extensions, and the one most flattering in photographs.
Watch for: Needs length to read as almond. On a short natural nail it becomes an oval with sharp corners.
Stiletto
A long taper to a sharp point.
Suits: An occasion. Photographs beautifully and is not built for a keyboard.
Watch for: All the strength sits in the middle. Dropped on a hard edge it snaps at the point, which is why it is an extension shape rather than a natural one.
Coffin
Tapered sides like an almond with the point cut flat. Also called ballerina.
Suits: Long extensions, and anyone who wants length without a point.
Watch for: The flat tip gives back some of the strength a stiletto gives away, which is why it wears better day to day.