This product is intended for fairing minor cosmetic surface defects before applying gelcoat or paint, as it is easy to sand to a feather edge once dry. It is not intended for structural or load-bearing repairs like floors or transoms. For structural repairs requiring strength and dimensional stability, you can use TotalBoat Polyester Structural Repair Putty, a high-strength, fibrous polyester putty for filling larger cracks and voids.