You can protect your form's design so that users filling out the form can not open or modify its form template (form template: In InfoPath, a file or set of files that defines the data structure, appearance, and behavior of a form.) in design mode (design mode: The InfoPath design environment in which you can create or modify a form template.).
- In design mode, click Form Options on the Tools menu.
- On the General tab of the Form Options dialog box, under Protection, select the Enable protection check box.