Unusual enclosures and tenuki variations
BobMcGuigan Many of the unusual enclosures come from standard joseki patterns (pincers, taisha, etc.) with the white stone removed. For example;
Charles A bad tenuki, though, since Black a is strong: see 3-5 point low approach one-space low pincer, tenuki. See 3563 enclosure for White attacking at a instead, the apparent vital point.
And
This was the start of An Younggil-Ch'oe Ch'eol-han (B) 2003-02-19. By the time was played, that corner looks like the 3-3 invasion of the 3564 enclosure.
But the previous diagram shows the usual invasion point.
Other ones of the patterns on unusual enclosures come from pincer joseki with the white stone removed:
In most of these cases of unusual enclosures, if White were to invade the black formation at a natural point it would result in a position equivalent to White having played tenuki against a pincer.