My first version of the insulated car battery pole shoes was connecting the power cable directly to the battery poles, so that some kind of external fuse was necessary to prevent a cable meltdown from accidental short circuit...

This new version incorporates a fuse holder right into the pole shoe. It uses standard a car fuse (e.g. 5, 10, 15 or 20A) - which are easy to find and only cost a few cents. One end of the fuse connects directly to the battery pole via a piece of stripped stranded 1.5mm2 copper wire. The other end of the car fuse remains outside the terminal and serves as spade connector, to which the power cable attaches via a standard 6.3mm female spade connector.

In principle, only one pole needs to be equipped with a fuse. So it's possible to combine a fused plus pole shoe of this version with an unfused minus pole shoe from the first version. However, I like to have spade connectors on both poles. Thus, I use the fused version for the minus pole as well (using a larger fuse, e.g. 30A).

Even though the pole shoes are labeled with "+" and "-", to avoid accidentally mixing up the poles I'd recommend to use red filament for the plus pole and black or green for the minus pole.

Note that the cone of the minus pole is slightly smaller than the cone of the plus pole.