This video shows locking the master link by sitting on the bike and put brakes on and push forward on pedal. (An alternative to using the tool)

Also shows taking it apart using the tool.

Bringing the link to the top in the big chain ring is what finally got the link to snap into place. Thanks for the tip!

  I suppose the time you need a chain tool is if an outside link has failed, but still attached to one end of the chain.