How to add Drop Down List to select a specific Dimension

[cwilliamson232RQ]

Say I have a C-Channel and the Length can only be 3'-0" or 6'-0" and I want to be able to only Select those two options from a Drop Down List. How can I do so in my Parameters? 

[ToanDN]

Change the Length parameter in the family to Type, not Instance. Then create two types, 3'-0" and 6'-0".

[cwilliamson232RQ]

What do you mean by show two types? Sorry I am a Rookie at this Parameter stuff. 

Maybe you can show me an example. 

Thanks! 

[Anonymous]

Create the family and call it 3' for example.  Load into a project and then duplicate it and call it 6'.  There should be a drop down list for the family.