An optical holder is a part used to fasten the element used in optical experiments, such as the polarizing plate, camera, or mirror and filter. Different sizes and shapes are available for the element. Select the holder suitable for the shape. In addition to matching the shapes, also be sure to check that the necessary fine adjustments can be performed to satisfy the optical system functions. As such, optical holder types are available that enable fine adjustment and angle adjustment, such as rotating types and tilting and rotating types, in addition to fixed types. Screws are commonly used to fix the holder, and most are made of aluminum.