4-5 10-3 enclosure

45103 enclosure  

This formation occurred a couple of times in games between Honinbo Retsugen and Sakaguchi Sentoku I (each time the enclosure was Sakaguchi's).

Trappy  

The idea is to play into the complex joseki with , having waiting.

3-3 invasion  

In this case the 3-3 invasion by White gives Black a fair result. But Black at a would already look overconcentrated.

Other way round (54103)  

The other direction of extension is rarely used now - White can get a good result invading at , as you can see by applying the joseki in the previous diagram. In this case ends up on a silly point.

Go Seigen did try this a couple of times very early in his career.

Coming in at a is asking for trouble with Black b. White would want to live quickly and avoid the trappy variation.