At endgame, is it usually possible to grab some mini-territory on an enemy corner already surrounded by walls? Maybe it's very tricky to do that before the enemy managed to kill you, but wondering if it's possible if the enemy responds correctly. I've lost large territories myself in such a way (enemy puts some stones in my empty corner and somehow managed to get two eyes). But maybe it's just because my responses was weak.

Just for the sake of argument, say white has 9x9 empty space on one corner, with solid wall on 2 sides and the edge of the board on the other 2 sides. Can I (black) smartly put some stones there and be alive?

You are asking a very broad question. Give a specific pattern and many here can help you.

Yeah, it's a general question. If we need a specific board. Say the corner of the board looks like this? (ignore the rest of the board)
Can I grab some corner territory as black?

It depends on the shapes and the player to move first. Sometimes, invasions are possible. If the territory has been built well, only reductions are possible.

I'm pretty sure that can live here :

Click Here To Show Diagram Code

[go]$$c
$$ ---------------------------------------
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . 1 . . . . . O. . . . . . . . . . |
$$ | . . . , . . . . O , . . . . . , . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | O O O O O O O O O . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Hi feldmarshall,
The rule of thumb is that the territory is secure when stones that surround it are on the 3rd line from the edge.

In your example, the stones are on the 9th line, therefore the territory is not secure at all.

The standard configurations to secure territory in the corner are
Whith 1 stone : third line third column (3-3 point, also called san-san, in japanese). It is the one shown by Tryss above.
With 2 stones : enclosure (shimari) from a 4-3 point (komoku) (C16 + E17, or C16 + E16)
With 3 stones : enclosure from the star point (hoshi) (C15 + D16 + F17).

In your diagram, if Black plays the star point (D16), White can still build an even smaller territory in the corner (starting with C17, then following the standard sequence).

The standard configuration to live on an edge are two stones on the 3rd line with two empty intersections between them (F3 + J3, for example).

In the beginning of the game, you take the four corners in turn, playing near, or on the star points.
Then you extend towards the edges playing either on the 3rd line, or on the 4th.
When you make a large extension from a corner (from Q16 to R10, for example), make sure that your new stone has enough room to make a further extension in both directions (from R10 to R13 and to R7), because your opponent might want to block you from one side and prevent you to make the living shape here.
This way, if you are blocked from one side (the opponent plays R12, for example), extend on the other side (R7), and you're safe.

It is pretty much impossible to live in there. The obvious starting point is the 3-3 point but even that has little chance. Of course, if white makes a mistake then he give black a chance. For example:

Click Here To Show Diagram Code

[go]$$c
$$ ---------------------------------------
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . 3 2 7 . . . O . . . . . . . . . . |
$$ | . 5 1 8 0 . . . O . . . . . . . . . . |
$$ | . 4 . 9 . . . . O , . . . . . , . . . |
$$ | . 6 . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | O O O O O O O O O . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code

[go]$$c
$$ ---------------------------------------
$$ | . . 8 . . . . . O . . . . . . . . . . |
$$ | . 6 7 2 4 . . . O . . . . . . . . . . |
$$ | . 9 1 3 . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O , . . . . . , . . . |
$$ | . . 5 . . . . . O . . . . . . . . . . |
$$ | . 0 . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | . . . . . . . . O . . . . . . . . . . |
$$ | O O O O O O O O O . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

_________________
Still officially AGA 5d but I play so irregularly these days that I am probably only 3d or 4d over the board (but hopefully still 5d in terms of knowledge, theory and the ability to contribute).

Even with wider moves like this?

Click Here To Show Diagram Code

[go]$$c
$$ ----------------------
$$ | . . . . . . . . O .
$$ | . . 3 2 . . . . O .
$$ | . . 1 . . 5 . . O .
$$ | . 4 . . . . . . O ,
$$ | . . . . . . . . O .
$$ | . . . . . . . . O .
$$ | . . . . . . . . O .
$$ | . . . . . . . . O .
$$ | O O O O O O O O O .
$$ | . . . , . . . . . ,
$$ -----------------------[/go]

Click Here To Show Diagram Code

[go]$$Wc
$$ ----------------------
$$ | . . . . . 4 . . O .
$$ | . . B W 5 1 2 . O .
$$ | . . B . 3 B a . O .
$$ | . W . . b . . . O ,
$$ | . . . . . . . . O .
$$ | . . . . . . . . O .
$$ | . . . . . . . . O .
$$ | . . . . . . . . O .
$$ | O O O O O O O O O .
$$ | . . . , . . . . . ,
$$ -----------------------[/go]

I'm not sure these are good moves, but Black now has two points he needs to cover. The only hope is that capturing the left side stone will work now, and I can't read that.

_________________
Occupy Babel!

This kind of case isn't very realistic. What's more common is that as external liberties are filled in, your opponent will leave a weakness, and you can live by either creating a seki in a small space, or capturing a stone or two and connecting to your outside group.

_________________
Occupy Babel!