Use this in conjunction with a vise grip to separate (open) a Shimano chain quick-link.

I needed to open my chain and didn't want to go and buy the special tool that I would only ever use once. You'll need to hold the chain so that the quick-link joint juts out towards you - to give you room to clip on the tool.

This tool does require a bit of finesse - so buying the proper tool would be better - but requires extra time if you don't have one.

FYI: you don't need a tool to close a quick-link - simply connect it up then position the quick-link just back from the chainring then press down on the pedal (with your front brake on). It'll snap/lock into position without much effort.

I printed it in PLA at 0.28 mm layer height on a Bambu Labs P1P with tree support.