Geometric Shape Options in Photoshop Elements
Geometry options help define how your shapes look. Click the downpointing arrow in the Tool Options in Elements to access the Geometry options described in the following.
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 proportion.

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: 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. This option is found in the Tool Options itself, not in the Geometry Options popup menu.
Ellipse geometry options
The Ellipse shape has the same options that are available for rectangles, except for the Snap 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:

Sides: Specify the number of sides for your polygon.

Smooth: Corners: Round off the corners.
Star Geometry options
The Geometry options for the Star shape are as follows:

Sides: Specify the number of points for your star.

Smooth: Corners: Round off the inner corners of indented sides or round off the corners.

Smooth:Indents: Determine the amount that the sides indent inward.
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 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.