Common millwright and machinist item.
Used in aligning motors/gearboxes, line shafts, shimming big bearings and scores of other things around machinery.
I have 5 rolls of various thicknesses on the shelf in my machine shop along with sheets of precise brass shim. Never know when it is needed.
Someone mentioned stainless shim. I have pre cut stainless steel shims used in machinery alignment, they have a U shaped cutout so you can slip the shim under motor or gearbox feed. Will post a photo if needed.
We use shims specifically made for shimming motors and bearings during laser alignment. They're shaped in a rectangle with a open slot in one end and a tab on the opposite end that's stamped with the thickness. They come in kits with different thickness, different kits are wider/longer for a larger footprint. Quicker than making new shims onsite, just loosen up the mounting bolt, lift up the foot and slide the shim in or out as needed. Sitll have to be careful that dirt isn't pushed into the stack up.
