What Controls Alignment Changing Width vs Moving Family

[BigPicture045]

What controls if the align tool changes the length parameter or if the parameters stays the same? I have seen some families change the parameter with the align tool and some that do not. 

SHELF

Before alignment:

After Align: You can see how the right edge of the shelf is no longer aligned.

[ToanDN]

It depends on the if you align to a reference plane or to geometry, and the dimension parameter associated with it (type or instance, locked or not).

[BigPicture045]

This shelf family uses all instance parameters. When I use the align tool, it moves the family. I can use the handles in a elevation view, however, I would like to be able to use the align tool to change the width parameter. Right now I can only use the align tool on one side, and then the other side must be moved manually. 

[ToanDN · Accepted solution]

Set the ref planes as Left/Right/Top/Bottom/Strong reference.  See attached (I have fixed the Left and Right planes).

[barthbradley · Accepted solution]

Use TAB-Select when picking the end to extend.   

Align vs Stretch | Revit | Autodesk Knowledge Network

[barthbradley]

.

[BigPicture045]

Thanks. Changing the reference to strong works and tabbing through and selecting the weak ref works as well.