Hi Everyone!
Just wanted to mention how to avoid an annoying issue that may rear it’s ugly head in this lesson. I only noticed this about 2 hours ago when “everything” was in place and I wanted to add some finishing touches, specifically- turning my Bishop’s notch to face me…
This issue may not affect everyone, but maybe someone… My version is 2.79.
I had a torrid time with the Bishop’s notch disappearing whenever I attempted to rotate it in any way AND it did not show up in the duplicated object- well, sometimes it did, most of the time it didn’t.
Prior to this, I had taken extra care to make sure my Normals were pointing outward- both on the notch and also on the Bishop piece. I also made sure there were no Doubles or extra geometry. Thirdly, I applied my Transforms - Translation and Scale.
Now obviously this wasn’t the issue. The next process did not solve the issue, but it solved potential issues that may crop up in future and I think it’s important to mention it here:
I went back to my saved Bishop-file to see if my geometry didn’t contain any “strays” or to see if there was anything wrong in the slightest.
I selected the Bishop-piece, went into Edit mode: Select->Select by Trait->Loose Geometry and one of the faces were shown to contain loose geometry. I could not see how, but something was wrong or “off” about it. I deleted the face, selected the edges around it and re-made it so that fixed that particular issue.
The following was actually the cause of the issue and also how I went about resolving it.
I had made my notch a child of the Bishop object in the Outliner- two or so lessons back- as Mike demonstrated and here was the issue:
In the Chessboard scene, I noticed that when you “Duplicate Linked” the Bishop, it actually does not duplicate the notch object, BECAUSE it’s hidden. You can confirm this by duplicating the Bishop and when you look over in the Outliner, you won’t notice the notch object in the duplicate.
I first had to make the notch object visible in the Outliner, select BOTH the notch object and the Bishop object, rotate them both to my liking and then “Duplicate Linked”. I then had to move the 2 duplicated objects separately to their square and then I hid the 2 notch objects from view again.
And Voila!
Phew! I usually talk too much, sorry! 
Hope it helps some poor soul out there! Have fun!