How can I easily stop users from modifying my application?

The minimum steps required to protect your application design are as follows:

1. For safety, first make a backup of your application
2. Open your application in Designer, using or creating a Designer (DSR) file
3. Select Application / Security Manager
4. Create a Group - for example: "OWNER"
5. Create a User - for example: "Boss". User "Boss" should be an administrator
6. Create another Group - for example: "USERS"
7. Create another User - for example: "User". User "User" can be an administrator or a manager
8. In Security Manager, make the group "OWNER" the only group that can design
9. Close Security Manager
10. Reconcile or Save as new application. (All users must be out of the application to reconcile)
11. Users log in as "User"

There must be at least one Group with Design Rights or you will be locked out of your application in SDesigner!