1.   But those bottles are, in a way, trail markers.

2.   Surfboard-shaped trail markers describe historic sites.

3.   They also said it had been a Native American trail marker.

4.   Zimmerman, who has an infallible sense of direction above ground, memorizes prominent features to use as trail markers.

5.   Buffalo that can spook teams roam the region, and wind can whisk away trail markers.