The most likely origin of “toe the line” dates back to the the late 17th or early 18th century when barefooted sailors stood to attention for inspection on wooden decked ships of the Royal Navy. The sailors lined up on deck along the seams of the wooden planks, hence to "toe the line".
I’m not standing for attention here, but I am standing next to the Blue Line. I previously posted some cool information about the purpose of the Blue Line.
Images by Katherine © 2013 CKB