A single joint can only cut an opening in a single face. To make a thru mortise, you need to create 2 joints, where each cuts into the opposite face. Just like in the shop - you cut from both sides.

Here's an example:


Here's a closeup, outside of the model:


The tip of the tenon is just simple geometry at the same level as the main timber. The housing and tenon are a standard joint component like always. The piece that's highlighted is the other joint. It's a flat (2D) object that I call a "cutter". CB.

thanks!

btw, how are you getting this view of sketchup??? It seems to me that sketchup will not export a view "from inside" as you show there, also I don't think it will export a view with selection highlighting.
??

first image is probably an exported jpg with x-ray turned on.
second view is most likely a screen shot with the component highlighted.

and, you can change how sketchup colors the section cuts, and the thickness of the lines in a section cut. check out the styles tool palette for more settings.

Correct on both. I had to resort to the old "alt|prt scr" technique. I suppose a video would have worked, eh? CB.

Is the final detail still accurate with this technique or is the tenon too short?

Not exactly sure what you are referring to with tenon length - but I think I can speak for Clark by suggesting that ALL joinery that you may see via SketchUp discussion, shared SketchUp components, illustrations in TFG journal's, etc - should be checked for the particular case / loading / species / etc. for the frame you are designing.

I'm talking about the tenon for the through joint. It doesn't extend all the way through, but does adding the "cutter" get reflected in the tenon detail. I'm doubting it does but thought I'd ask.

the "cutter" is 2D, so does not add length.

yes, the cutter is only 2d, but the tenon could be whatever length needed, as shown here in clark's image.