Are there any josekis for a two point jump on the third line, such as the white group above? I often hear this described as a base, but I don’t see how to ensure two eyes. Any references or advice gratefully received.
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In my inexpert understanding, the ‘two-space jump = base’ idea is a rule of thumb suggesting that in this situation white can be fairly confident of making two eyes if attacked. This confidence should diminish if black has more stones in the surrounding area.
There is a page at Sensei’s Library showing how white would defend against a black play at J17:
In the example you showed black probably wouldn’t attack the white base directly because there are bigger moves elsewhere. Black might play O17, for example, checking the expansion of the white group and increasing the security of the corner. (Similarly white wouldn’t usually play this way in the opening because black is taking the corners.)
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The shape doesn’t ensure two eyes in general because of
However, unless it is completely surrounded, it is hard to kill.
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Stepping up a level, asking “How do I ensure two eyes?” is not the right question. I guess you are concerned about your group living. Your stones will die if Black can capture them, otherwise you will live. Are you really concerned that their two stones will capture your two stones? If there were also Black stones at F17 and N17, say, you might want to jump out to stay healthy.
There are a few standard followup sequences that can happen if Black has stones nearby, like them trying to seal you in or scoop out your base. But the position will have to get more concrete first.
Two stones on the side like this is a good flexible start towards the future. In the future, you might spread out more along the side, you might expand into the center, you might use this as strength to push a weaker Black group into. Your stones are close enough together that they can work together if Black tries to play very close, but far enough apart to be productive. If you start thinking about how to make your two eyes just to be sure, you’re going to be playing very slow and inefficient moves out of fear while Black is much more ambitious.
Apologies for not really answering your actual question (hopefully other people are taking care of that), but I wanted to make sure you understood the bigger picture, since getting hung up on “Where are my two eyes?” is a common issue early on, and it can be hard to overcome.
(And an edit to add: as garlicsoup says, White wouldn’t even play L17 right now, it’s too small! But that’s another discussion.)
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If Black approaches at F17 it would be normal to play o17. If Black approaches at N17 there is not an obvious response. F17 would be too small, so a tenuki(play elsewhere) would be natural. If then Black plays F17 it would be normal to jump at H15 or L15.
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Without any approach move it’s said to be a base.
If there is a move from your opponent nearby you usually add a move, be a knight move on the side (kind of miai extension) or a one space jump into the center (if both approaches already from each side).
What you are asking is the typical stuff missing between what you can find in a book and what you can read at DDK level. Things that you’re supposed to explore and find by yourself.
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Yeah, I guess I’ll pick it up in due course.