Grinding machines and oscillators are a versatile range of power tools used to smooth or cut various types of materials. These hand-held tools are compact enough to be used in hard-to-reach places, and many designs have disk heads that are shaped to reach into corners. Sanders and grinders are used to smooth down surfaces and come with different types of grinding disks designed for specific materials such as plastic, wood or stone. The abrasiveness of the disk is graded according to how much material needs to be stripped from the work surface and how smooth the finish needs to be. Oscillators are multifunction tools that have a wide range of attachable tool heads designed for specific jobs and materials. Depending on the attachment, they can be used as a sanding tool but are also designed to cut materials such as wood, metal or stone, and even gouge out waste material. Unlike hand-held power tools, disk grinders or bench grinders are intended to be securely attached to a stable surface, while the material that is worked is held against the rotating wheel. Interchangeable wheels make this equipment ideal for sharpening metal blades, removing rust or sanding surfaces.