Dimension below part.

Examples show a dimension on the upper edge of a polygon.
The length of the upper side of a rectangle for example.

How can the lower edge be dimensioned so that the dimension
line is below the figure rather than superimposed upon it?  
Negative values for the extension line extension and offset don't help.

Thanks,                     ... Peter E.

Do you mean like this one?

Nice.  Thanks,           ... Peter E.

"Snap endpoints" or "Snap intersection" was constraining the location of the dimension.  With "Snap free" the location was unconstrained.  Documentation could mention that Snap can constrain the location of a dimension.                  ... Peter E.

I added: "Enable Free Snap along with Snap Endpoints."
as step one here: http://wiki.librecad.org/index.php/LibreCAD_users_Manual#Dimensions

Is that what you were thinking?

> Enable Free Snap along with Snap Endpoints.

Definitely that helps.  Thanks.  

Now a new question.  The menu here shows "Snap > Free" and "Snap > Endpoints".
Appears that when one is activated, the other is always deactivated.  In the
graphical display, only one of the menu items appears recessed.  Therefore,
what is meant by "Free Snap along with Snap Endpoints"?

Thanks,                ... Peter E.

That has been fixed recently. However, you would have to build from source code. It's about time for another Nightly build really, there has been a lot of improvements.

There is a new nightly build for Windows.

https://sourceforge.net/projects/librecad/files/Windows/NightlyBuilds/