Cassandra looked around and saw a bunch of small rocks near the edge of the river, walked over to it and gathered them in her arms. then she started to build a fence around her tent with the rocks. When she had finally surrounded her tent with little rocks she consulted her list of runes and started to carve it no the rocks in a pattern

Thurisaz
Uruz
Kaunan

When she was finished, Cass looked it over and thought about why she chose the three runes.

Thurisaz: Dark Forces. What better way to keep her safe than to scare away her attackers?
Uruz: Strength and Power. she was going to need it to stay protected without her wand.
Kaunan: A new day, fire, light, Protection. It was fairly obvious wasn't it? Protection.