The options for a valve relate to its shape, and the positioning of attached words (defined rates).
Shape
Valves can be vertical and horizontal bow ties, vertical and horizontal I beams, a circle with a cross through it or invisible (the last option). This allows you make you to customize the appearance of your diagram to meet your needs. Invisible valves are useful for naming rates or other concepts without added visual complexity.
Valves can be resized by dragging the handle in their lower right hand corner. You can set the initial size of valves from the Options dialog.
Attachment
Attachment determines where the variable attached to the valve is placed. You can name a valve by clicking on it with a Variable tool or using the Merge tool to merge an existing variable onto the valve. When a valve is named, it moves whenever the name is moved.
The attachment positions are below, above, left and right. Note that the orientation of the word needs to be changed from the word options.
