Hi,
I'm new to SketchUp having come from a SolidWorks background. If you look at the screen shot attached you will notice that at the cursor there is a dimension of 5" from the top of the square hole to the top of the part. It appears SketchUp will not place this dimension here! I can't see what is wrong with this. Instead it wants to dimension from the left side of the part to this point -- -- with a dimension of 10" parallel to the horizontal axis instead of 5" up and parallel to the z like I asked it to.

It's causing Dimensioning Dementia