I just purchased a DC shunt tool from briggs

[Rustynuts]

Any pointers on potential uses of this tool?

[Arkie]

Yes: Make sure that the connections on each end of the shunt are really secure or you will get wrong readings readings.

A more user friendly method (and faster) for checking DC amps zero to 400A is with the use of a clamp around meter such as a UEI DL49 digital meter. (about $100 new or can find good used ones on flea bay for $25 to $50 with care)
(their are others but my point is no connecting a shunt just open jaw and clamp on and read)
Also works on AC amps to 400, will automatically turn itself off if no reading after awhile. Really fast for checking stator output amps, starter draw, alternator output amps, for small engines and autos, etc.
Just be careful when shopping for a DC meter because not all will read DC amps to 400 automatically with a clamp around jaw. (even some high dollar $1000 flukes require special optional adapters that costs more than a UEI meter)

Shunts were common before later model clamp on meters came to be.