How do you put a text under a dimension line? No, I’m not talking about literally putting a Text under a dimension line using the command Text or Mtext then putting it under the dimension line manually. What I’m talking about is how are you going to a put Text under a dimension line automatically, without doing any command other than DIMEDIT or Edit.

Here is how, after a dimension was made in the object in your drawing, key-in command DDEDIT or just ED. Then click the text on the dimension line and add a backward  slash and a capital X after the dimension text (\X your text here). The result will be like those on the picture below (Fig.1).

(Fig.1)