One was that you can never know too much about the shadow line and the people who walk it.
He drew in suddenly, ten feet short of the shadow line.
Then he crossed the shadow line, and the blast of the sun's heat struck him.
The lowering sun was picking up his trail with a shadow line, too.
That changed when they stepped across the shadow line.
At the shadow line he hesitated, as if to plunge in would trap him there for all time.
The shadow lines on a specific block give the same show, down to the day, hour and minute, year after year.
That shadow line, indetectable in air, now lay sharp across the water behind him.
He picked up a bigger rock and threw it at a shadow line twice as distant.
A shadow line of black appeared around him, outlining him for a second.