How to align region borders? Back in the old days, it was fairly easy to merge windows. They moved in regular steps of x pixels and they always lined up. 

For quite some time now I sometimes experience situations like this:



Since they don't line up and the movement seems too coarse, it's impossible to merge the horizontal regions. What to do?
And just as I was typing a few days ago, I thought to try out ctrl and yes, ctrl does the trick. Just hold LMB on a border and then add CTRL.