Fuses have often mystified me as to not so much what they will carry in Amperes but at what current they will 'blow'. There are an overwhelming types of fuse so I will focus on 12 Volt automotive standard blade that hobby radio enthusiasts are most likely to encounter e.g. Icom & Kenwood transceiver heavy duty power leads.

They are colour coded for rating in Amps usually 3 A to 40 A. Generally speaking a fuse will blow at 15 X it's rating. Therefore a 10 A rated fuse will likely blow at 15 A. How do I know this? I don't... I made it up.

But then I surfed onto the link below that states an automotive fuse will likely blow at 2 X it's rating. Comments welcome.

BTW Early pioneers would whittle down a thick connecting wire down to a small section of thin to protect equipment e.g. early long distance telegraph wires.