Thresholds (sometimes called baby thresholds, end caps, and square noses) can serve many purposes. The threshold caps off the floor and creates a barrier between the bamboo flooring and either a higher or lower floor. Typically you would want to use a threshold for an exit doorway like french doors or a sliding glass door. Thresholds even have a symbolic meaning in some cultures. For example it can be seen as bad luck to shake hands over a door's threshold.