Material: PLA though any rigid material should work. Use: Single use Shield Assembly: Many thin plastic sheets, lamination sheets, or even transparencies should work. The above STL is designed for letter sized paper with 4.25" triple hole spacing, the standard for the USA and Canada. My hole puncher is an ACCO 20 that produces ~7mm holes in the plastic. If your holes are larger or smaller, use the Onshape file to modify the dimensions to suit your needs.