A friend uses shears like these (much less rusty than these :) ) to cut cable marker tags when he does electrician work, but he sometimes has difficulty with cutting all of them the exact same length.

So I designed this magnetically attached stopper with four different distances from cutting edge (10mm, 15mm, 20mm, 25mm). You can easily attach the tool (since it's magnetic) and rotate it to select the right length.

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