Build update:
I use roof flashing for the metal backing on terrain that I intend to use for magnetized accessorizes. The thickness of the material I used on this build is 0.0115". I recently invested in a Grizzly T26470 12" hand shear. However, I have been using extra long tin snips from Craftsman for sometime without issue. I purchased the Grizzly to cut long thin pieces to be installed along the side of walkway. Cutting 0.125 - 0.25 inch strips with the tin snips is not practical. Tin snips could have been easily used on this build. I have purchased a 19" x 50' roll of flashing for larger pieces, however I really like the 5" x 7" rectangles for this type of build.
BTW, the hold down clamps on the Grizzly shear are something I added. The shear is not fitted with the hold down feet found on more expensive models, so I added these clamps.