This is the rope attached to the shrine bell of Kume Suitengu (see yesterday's post). Many people who come to pray here use this rope to ring the bell. It's a way to announce their presence before their time in prayer.
You can see in the photo bellow that many people have swung this rope around to ring the bell.
There is usually a offering box under the bell, where people toss in their coins. At the shrine the method of prayer after ringing the bell is: toss coin, two bows, two claps, pray, then one last bow.