# 2.2.3: Add Supports

Supports define how a structure connects to the ground. They suppress translations or rotations at nodes. An activated button appears black and means either zero translation (T) in the direction of the global x-, y- or z-axis or zero rotation (R) about the corresponding global axis (or local axis if you input a plane). A node index or position can be used to specify the location of a support. Supply a plane as input for specifying locally oriented support conditions.

{% hint style="info" %}
Green arrows symbolize translational supports, purple circles stand in for rotational supports (see fig. 2.2.3.1).
{% endhint %}

![ Fig. 2.2.3.1: Supports specify how a structure interacts with the ground](https://442610158-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MCkDlhlZpqUmakSqOrp%2Fsync%2F700322f9426a6a742c80b678c995472f9dde08d0.png?generation=1595316044084328\&alt=media)

For static analysis, a structure needs to be supported in such a way that it can not fly around freely. In three dimensional space, a rigid body has six modes of movement or degrees of freedom (DOFs): three translations and three rotations (see fig. 2.2.3.2). Thus there need to be at least six support conditions in a structural model to fix it. When a model or parts of it are moveable, the **“Analyze”**-component either refuses to calculate or returns huge displacements. Should you encounter a problem like this plug your model into the **“Eigen Modes”**-component. It can detect the rigid body movements which cause the problem.

![ Fig. 2.2.3.2: A body in space has six degrees of freedom (DOFs).](https://442610158-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-MCkDlhlZpqUmakSqOrp%2Fsync%2F4896fe8d03cebe3dc5d74f5a6eae5fec2e41ddb4.png?generation=1595316031273523\&alt=media)