Bearings

In 2D, we have 3 degrees of freedom (DoF): Translation in x, translation in y, rotation around z.
In 3D, we have 6 DoF: Translation in x, y, z. Rotation around x, y, z.

Bearings in 2D

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Roller Support: DoF = 2
Pinned Support: DoF = 1
Fixed Support: DoF = 0

Notice that every free degree means a locked degree. If the DoF = 0, there are 3 locked degrees.