Models with the Strider special rule are rare – normally, they will have a subset of Strider, such as Forest Strider or Marsh Strider and the rule only applies in terrain of the specified type. Models with the Strider rule treat that piece of terrain as open ground for the purposes of Movement, meaning they ignore any Movement penalties or Dangerous Terrain tests otherwise caused by it. Note that they still follow the rules for that terrain type in terms of combat.