Getting dimensions to snap accurately on drawing. (almost solved)

I have never been able to get dimensions to snap on corners of an entity accurately and still be able to extend the dimension off the drawing.
I can use the snap function and get it to dimension to the fourth decimal place accurately. However, when I do it this way, the dimension is not extended outside the drawing itself.
Have I missed something? Can someone assist please? I have the latest version of LibreCad installed.

Be sure to have "free snap" enabled too, so you can place the dimensioning line somewhere off the object.
You can also switch to "Ex"(exclusive snap mode) during the operation, after having set the reference points. This disables the other snap settings but still keeps them remembered. But be aware it automatically activates "snap to grid".    

Excellent dellus, I got it to dimension accurately. Thanks.
However, I did not understand this:

"

dellus wrote

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You can also switch to "Ex"(exclusive snap mode) during the operation, after having set the reference points. This disables the other snap settings but still keeps them remembered. But be aware it automatically activates "snap to grid".

Can you explain further please?

Forget what I have said about exclusive snap. I have realized now that I didn't understand its working at all, haha. I thought it allowed to toggle between a set of snap modes and none, but no, it's between a set and a single selection. Sorry, hope I have got it right now.  

Ex ON = only one snap mode can be selected -- activating another mode deactivates the current mode
Ex OFF = normal mode, where all snap modes are allowed at the same time

The activated snap modes are remembered for the ON and OFF states.

ravas wrote

Ex ON = only one snap mode can be selected -- activating another mode deactivates the current mode
Ex OFF = normal mode, where all snap modes are allowed at the same time
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Where do I find the "Ex" selection?

It's in the 'Snap Extras' category of the toolbar/menu creator.

Sorry Ravas, but I still cannot find "Snap Extras". Please provide more instructions.

It's only available in 2.1.0+
https://github.com/LibreCAD/LibreCAD/wiki/Widgets

Thanks ravas. That explains it.