Just dip the toilet paper in water until your fingers will drip, and then stick it on the hole of the shaft to let the water moisten it into the shaft.
It will last for a few days. Pay attention to step one. When the toilet paper is dry, add water. Be careful not to add too much water. Do not flow to the position of the shaft pit. Only wet the position of the shaft pit, so that the shaft will absorb water and expand.