A material designed for creating a custom-made beam block used to size, shape, or control depth of penetration of a beam of radiation delivered to a patient during radiation therapy treatments, to limit or eliminate exposure to non-target body areas. Beam block material is either: 1) a highly attenuating material, e.g., lead, cerrobend (Wood’s metal), or Rose's metal (aperture type); or 2) a material such as acrylic or wax that can be used to control the beam energy delivery depth. It can be cut or moulded into specific configurations to shape/define/attenuate the radiation beam, and is typically remelted for reuse after the patient treatment is considered finished.