I have watched some 19x19 games played by pro’s. I noticed that most of the time the players don’t play on the outermost lines, can someone explain to me why?
I can think of three main reasons:
The outer line has virtually no influence on the rest of the board. If you place a stone there, it does not give you a stronger position in the middle of the board, while a stone on the 4th line can give you a lot more influence on the rest of the board.
It’s easy to capture, since it has only three (or in case of the corners, two) liberties, instead of the usual four. This makes it more vulnerable to be exploited:
See for example here how white can push down the black stones, that have nowhere to escape. Such a thing is a lot harder in the middle of the board.
Probably most importantly, it’s very inefficient in surrounding territory. The only thing a first line stone can do is to nudge the boundary of territory one or two points in favour of one of the players. Compare:
This makes it a very small gain compared to what you could do with that move on other places on the board. Because of that, your opponent should almost always ignore you when you play a first line move: there are other places on the board that are more important to play, than to protect that single (or relatively few) point(s) that you are trying to get with your first line move.
Generally in the first 50 or so moves, try to find places that help in securing at least 10 to 20 points of territory when you have the initiative. If you’re protecting things worth less than 5 points, you’re better off ignoring it. Of course, as the game progresses, less and less points will be up for grabs, and the smaller moves will become more and more important. First line moves are usually one of the last to become important.
There are some exceptions where first line stones are very useful early in the game, and that is in life & death problems, especially involving throw-ins. Sometimes it’s necessary to play on the first line to keep your group alive or to kill your opponent’s group. In those cases it can be the largest thing to play on the board.
When you build your houses on the board think the edges like the walls and the stones like pillars. It’s useless to put the pillars glued to the walls.
If it goes to endgame, they will play on the first line!
When pillars doesn’t matter anymore, time to close doors and windows.