Specify Geometry Options for Your Photoshop Elements 10 Shapes
Geometry options help define how your Photoshop Elements 10 shapes look. Click the downpointing arrow on the Options bar to access the Geometry options. You can choose among Rectangle and Rounded Rectangle, Ellipse, Polygon, Line, and Custom Shape Geometry options.
Rectangle and Rounded Rectangle Geometry options
Here are the Geometry options for the Rectangle and Rounded Rectangle shapes:

Unconstrained. Enables you to have free rein to draw a rectangle at any size or shape.

Square. Constrains the shape to a perfect square.

Fixed Size. Lets you draw rectangles in fixed sizes, as specified by your width and height values.

Proportional. Allows you to define a proportion for the rectangle. For example, specifying 2W and 1H makes a rectangle twice as wide as it is high.

From Center. Enables you to draw from the center out.

Snap to Pixels. Aligns the shape to the pixels on your screen.

Radius. For Rounded Rectangles, applies the radius of a circle used to round off the corners. Note that this option is found on the Options bar itself, not in the Geometry options dropdown menu.
Ellipse Geometry options
The Ellipse shape has the same options that are available for rectangles, except for the Snap to Pixels option. The only difference is that, instead of being able to create a perfect square, you can create a perfect circle with the Circle option.
Polygon Geometry options
The Geometry options for the Polygon shape are as follows:

Radius. Enter the radius of a circle used to round off the corners of a polygon when you have the Smooth Corners option selected.

Smooth Corners. Round off the corners.

Star. Create an inwardpointing polygon called a star.

Indent Sides By. Determine the amount that the sides indent inward.

Smooth Indents. Round off the inner corners of indented sides.

Sides. Specify the number of sides for your polygon or the number of points for your star.
Line Geometry options
The line’s Geometry settings include whether to put arrowheads at the start or end of the line. You can also adjust the width, length, and concavity settings to change the arrowhead shapes.
Custom Shape Geometry options
The Custom Shape options are similar to those you find for the other shapes, but with a couple of unique options:

Defined Proportions. Draws a shape based on the original proportions you used when you created it.

Defined Size. Draws a shape based on its original size when you created it.