Well, as my screenshot shows, there is a back board and on the front there is a row of strips. Now I want to measure the distance between the right side of the last strip and the right side of the back board. How can I do that?
Okay, I got it. Thanks. 
What was the solution? All I see is “Ok, I got I it. Thanks.”
The solution is at the bottom of the modeling space 
Nope, for me there are - unfortunately - no 2D drawings! However, as you mentioned, I selected the two faces (right face of back board and right face of last strip). Then the distance is been shown at the bottom of the screen.