Unidirectional System:
(a) Dimensional values shall be indicated hence such they may be read from the bottom of the drawing-sheet. Non-horizontal dimension lines are preferably near the middle, interrupted, hence the value may be inserted.
![1975_Unidirectional System.png](https://www.expertsmind.com/CMSImages/1975_Unidirectional%20System.png)
(b) Angular dimensional values may be oriented also like in diagram.
![503_Unidirectional System1.png](https://www.expertsmind.com/CMSImages/503_Unidirectional%20System1.png)
(c) The positioning of dimensional values frequently requires adapting to different conditions. Hence, for example where values may be:
(i) Close to a termination to ignore having to follow a long dimension line whereas only part of the dimension line requires to be displayed.
![1351_Unidirectional System2.png](https://www.expertsmind.com/CMSImages/1351_Unidirectional%20System2.png)
(ii) Above the extension about the dimension line beyond one of the terminations, and space is limited as shown in diagram.
![287_Unidirectional System3.png](https://www.expertsmind.com/CMSImages/287_Unidirectional%20System3.png)
(iii) on the ending of a dimension line that is too short for dimensional value to be indicated in the common way
(iv) On top of a horizontal extension of a leader line such terminates on a dimension line whereas space does not permit a placement at the interruption of a non-horizontal dimension line.
![562_Unidirectional System4.png](https://www.expertsmind.com/CMSImages/562_Unidirectional%20System4.png)
(v) The given indications are used along with dimensions to display applicable shape identification and to develop drawing interpretation. The applicable indication or symbol shall precede for dimension the value.
f : Diameter
Sf : Spherical diameter
SR : Spherical Radius
R : Radius n : Square
![793_Unidirectional System5.png](https://www.expertsmind.com/CMSImages/793_Unidirectional%20System5.png)