It's an old trick called "stringing" trails. You don't need monofilament, just white sewing thread. Tie one end to a shrub and drape a length across the trail. As the deer passes, the thread will play out in the direction of travel. Only you don't wait a week. If you lay the thread in the evening, you check it later the next morning to see if they're using the trail in the evening or morning. To reset just re-lay the thread back across the trail. Before scouting cameras, it was a good way to pattern deer movement.