Surfaces that are frequently wet or that would be dangerous or inconvenient if slippery are often given special treatment to ensure a non-slip finish. These finishes can be achieved by hand tool techniques, by sawing, by applying an abrasive aggregate, with epoxy resin materials, and by setting non-slip strips in the concrete. Troweling is the easiest way to obtain a non-slip surface, but it is probably the least durable. Depending upon the degree of slip resistance required this method might consist of merely discontinuing troweling after a wood floating operation to produce a gritty surface or swirl troweling to raise ridges on the concrete surface. Where foot traffic is to be heavy or for industrial vehicle applications, it has been found advisable to use abrasive grains in the surface of concrete to provide a long lasting non-slip surface. The two most popular base materials for these non-slip abrasive grits are silicon carbide and aluminum oxide. The extreme hardness and sharpness of the abrasive grains when embedded in concrete result in an effective abrasive action, which in turn produces long-lasting slip resistance. In recent years, sawing has been used to produce a slip resistant surface in hardened concrete. This technique is usually employed when conditions prevented application of a non-slip surface at the time of casting or when discovery of the need for slip resistance is made after the concrete has hardened. Etching with acid is another technique that may be employed in cases where it is necessary to achieve a non-slip finish in hardened concrete. Another technique for achieving an anti-skid texture on already hardened concrete surfaces is the application of compounds that are subsequently textured and hardened.