Left Two Thirds Block

It fills the left two thirds of a character cell. In text graphics, it supplies one solid tile; the grid around it determines the picture.

Think of a fixed text grid: the mark paints a rectangle across most of one cell, leaving the rest open.

What did HP use this character for?

It belonged to a set for drawing forms and grids. HP's June 1975 account of the 2640A describes an optional line-drawing set for forms, grids, and graphs. Its microvector characters—small line pieces designed to meet cleanly across cells—let those shapes join into larger pictures.

This glyph corresponds to position 24 in the HP 264x line drawing set. On the 2640A, that set was selected separately from the standard Roman set (the terminal's usual Latin letters).