The cement composition should contain any adhesive substance (of your choice). Next, with this composition, we fill in the liberated cavity of the element and all existing cracks, and small potholes. After the neat distribution of the cement mortar over the entire surface of the windowsill, it must be covered with polyethylene in order to let it completely clasp and dry for three days.As well as polyethylene will serve as a kind of protection against rain water.