Length of extrusion in family editor not adjusting

[mgmueller]

I created a framing member family using a copy of a family that worked perfectly.  It works in every way except the length, which will not flex in the family editor and therefore when I load it into the file where I want to use it, it is always 10' long.  

Above is a screenshot from the part I am trying to make.

Below is a screenshot from the part I started with.

What am I missing?  I'm sure it's something simple but I haven't been able to find it.

Thanks for any help.

[ToanDN · Accepted solution]

Select the extrusion, drag each end grip to a ref plane and lock the pad lock.  Place a dimension between the ref planes and associated it with an instance length parameter.

[mgmueller]

Thanks, I found the correct padlock!