You tie your shoelaces into a firm bow before heading out. The knot holds the laces tight around your foot, keeping the shoe snug with each step you take.
As you walk, the laces flex and shift with the motion of your foot. The bow remains secure, maintaining its shape and grip.
The threshold arrives the instant the bow unravels completely. The loops loosen and the ends pull free in a single motion.
Before this point, the shoe stays fastened securely. Right after, the laces dangle loose, and the shoe slackens around your foot with every stride.
The footgear that was once locked in place has crossed into a state of looseness, ready to slip with the next step.