While it looks rather sparse, the Entity Info box is perhaps the most often used dialog in SketchUp.
Experienced modelers tend to leave Entity Info open while they’re modeling.
Primary among its many functions, Entity Info tells you the name of a selected entity.
Experimenting with Entity Info will help you learn about the SketchUp entities you’re working with.
Click … Window > Entity Info and then draw some shapes.
A circle with the Circle tool
A polygon with the Polygon tool
A rectangle with the Rectangle tool.
Now click on the edge of each shape with the Select tool and see what Entity Info has to say.
No surprises here. That is, until you click on an edge of the rectangle and find Entity Info only says ‘Edge’
So what happened to the Rectangle entity you just drew?
Well, odd as it may seem, there is no rectangle entity in SketchUp.
The Rectangle tool is just a fast, accurate way to draw four co-planar Edges (lines) at right angles.
Thus, whether you draw a rectangle with the Line tool or the Rectangle tool makes no difference in terms of the resulting geometry. It’s all the same and so has no relation to the problems with your roof.
It’s not clear which tutorial on inference you’re referring to; there are many.
And it’s difficult to determine where things are going wrong from just a screenshot.
Share a model with the roof triangle setup the way you describe.
Stop and save the model in the state just prior to erasing and the subsequent Push/Pull operation.
Attach it to your reply and we’ll have a look.