The chain quick link is made by SRAM and also KMC, and I think there are a couple of other brands making quick links too. The one that I am using is the KMC MissingLink, which is compatible with Shimano chains.
KMC MissingLink for Shimano 10 speed chains
To install or remove this chain link, it is possible to use hands to connect or disconnect it. However, I find that it is much easier to use a tool for this as they can sometimes be too tight for the fingers to open the link. Some pictures showing how it is used can be found at this blog post.
I was previously using the KMC Missing Link Chain Pliers, and they work pretty well at disconnecting the chain quick link. However, I find that sometimes it can be quite difficult to join back the chain, as I can't make the quick link sit into place properly even when I push hard on the crank.
Came across this Super B Master Link Pliers, which has 3 claws that ingeniously connects and also disconnects the chain quick link.
Can be found at Scootz, Bukit Merah branch.
Designed to disconnect and connect chain quick links!
At rest, before activation. Note that the left side is for disconnecting the chain, and the right side is for connecting the chain.
When the handles are squeezed, one side of the plier closes, while the other side opens! The side that closes will disconnect the chain, while the side that opens will force the quick link into place.
My old KMC Missing Link Pliers, still working well.
Simple and functional construction.
With the purchase of the new Super B Master Link Pliers, the KMC Missing Link Pliers is now redundant. If anyone is interested in it, let me know!