A sashikomi is a thrust into an enemy
formation that touches three enemy stones.
is a sashikomi that threatens to cut at a
In Nagahara's Strategic Concepts of Go it is
also called insertion. The one above is used
as an example for a probe:
Black just approached (tsume), threatening an
invasion at a. White could defend at b,
but has a better option: probe at c.
If Black connects inside, White defends and can
later exploit the weakness (aji) at a.
If Black connects outside, White plays forcing
moves (kikashi) until the weakness at a is
gone, allowing White to grab the initiative
(sente) and play 11 elsewhere.