Gauging Trowel - Economy This gauging trowel is used to transfer plaster from the mixing bucket to the wall. This gauging trowel has a rounded point, which allows small quantities of plaster or render to be selected, whilst the flat surface of the trowel can be used to spread the plaster or render evenly and smoothly across the surface. This gauging trowel comes with a rubber handle to ensure maximum grip and comfort.