A vertical line inside the drying square, meaning hang to dry.
A single vertical line inside the drying square means hang the garment to dry. The lines are read as the garment on a line, which is why a horizontal line means dry it flat instead.
In the ISO 3758 system a vertical line inside the drying square instructs the garment to be hung to dry rather than tumbled.
Contexts: Laundry
A square outline containing a single upright stroke running from near its top edge to near its bottom edge.
A vertical line means hang to dry and a horizontal line means dry flat; the orientation of one stroke is the whole difference.
Both are built from squares, and both are used in laundry contexts.