Shims are thin pieces of material, usually metal or plastic, used to fill small gaps or spaces between objects. They are commonly used in construction and engineering to level and align components, such as door frames, window frames, and machinery. Shims can also be used to adjust the fit of parts in a joint, to reduce vibration, and to provide support. WEDGES are similar to shims, but they are thicker and have a tapered shape. WEDGES are used to split materials apart, such as logs or rocks, and to hold objects in place.