Enclosure opening - high variant
The variant of the enclosure opening with a high enclosure was explored ahead of the version now considered standard. This diagram is probably the classical idea: White approaches low in the right corner, Black's pincer (square-marked stone) combines well with the circle-marked stone to build a framework.
These days White is more likely to play the high approach White 1. What now? The pincer at a is one plan that is reputable; the pincer at b isn't so highly thought of, for reasons of joseki choice explained on the enclosure opening page.