Shielding refers to the ability of a material or structure to attenuate electromagnetic waves from one region of space to another. This thesis looks at the design and construction of a door and frame assembly to improve its shielding effectiveness (SE) to meet the minimum specification of 50 dB from 1 GHz to 28 GHz. This is accomplished by first looking at the choice of materials and construction of the assembly. To predict the performance of the design chosen, ANSYS HSSS (EM simulator) is used to look at the SE of the structure in an ideal environment. Shielding effectiveness measurements are performed on a miniaturized version of the design in an anechoic chamber. The performance of the final design is tested at Raymond EMC. This is accomplished by installing the full-size structure in an enclosure rated for 100 dB and performing the SE measurements in accordance with IEEE 299 standard.