# Revision history [back]

I figured out what I was doing wrong here. When I tried to specify a link to the world, I didn't specify the model name.

A link like the following will prevent the link named base of a model named arm from moving relative to the world:

<link name="world_fix">
<parent>world</parent>
<child>arm::base</child>

Placing this in the root of your <model> will then prevent the base from moving.