I think you mean "strongly named" assembly. Sign it. See project properties, the "Signing" tab.
I would strongly recommend to do that for every single assembly deployed to the users in the form of PE files without source code. This operation costs next to nothing but is very useful in several respects. Besides, if you reference the unsigned assembly (not as a "Project" of a solution) and later decide to sign it, you will have to redo the reference in referencing assemblies; and that would be a waste of time.
Also, take a look at this CodeProject article: Strong Names Explained