Complex sentence: A group wishing to paint the Fence must station two representatives on the small gravel region surrounding it; so long as two guards remain within the boundary, no other group may "take" the Fence.
Split into simpler sentences: A group wishing to paint the Fence must station two representatives, or "guards", on the small gravel region surrounding it. As long as two guards remain within the boundary, no other group may "take" the Fence.