# Revision history [back]

### A correct way to implement "fixed" joint?

Am I right that there is no fixed joint type in SDF similar to one in URDF? So how should I implement one?

In one of the tutorials Hokuyo laser is attached to a mobile platform with revolute joint, but with zero limits:

<joint name="hokuyo_joint" type="revolute">
<parent>chassis</parent>
<axis>
<xyz>0 0 1</xyz>
<limit>
<upper>0</upper>
<lower>0</lower>
</limit>
</axis>
</joint>


Same approach is used in Simple Arm model, to attach it to the ground.

Although it seems ok, but there is an extra joint control on Joints pane which of course does not control anything. Also there is an extra coordinate frame marker in scene.

So is it the only way to implement fixed joints?