# Surface Side

### Glossary Term

000123

Each surface has a positive surface side as well as a negative surface side.

Since a surface is a 2D object whose thickness is considered a physical property, the results are displayed either on the positive or the negative side.

###### Orientation

The position of the positive or negative surface side can be controlled by the local axis system of the surface: the positive surface side is the side in which the positive z-axis runs. The negative surface side lies in the direction of the negative z‑axis. You can activate the axis system of the surface using the "Display" navigator (see Figure 01).

###### Graphical Check

You can use the "+/- z-Surface Side" option to check the position of the surface sides (see Figure 02). It is important for the definition of foundations with failure or also for a reinforcement layout. The top side of a surface is shown in red, the bottom side in blue.