Dots inside a circle in a square, setting tumble-dryer heat.
A circle inside a square is the tumble dryer, and dots within the circle set the heat: one for low, two for normal. No dots means the garment may be tumbled at any heat.
In the ISO 3758 system a circle within the drying square denotes tumble drying, and dots inside the circle set the permitted heat level.
Contexts: Laundry
The square means drying generally and the circle inside it means tumble drying specifically, which is why a square with no circle is a line-drying instruction.
Contexts: Laundry
A square containing a circle that nearly fills it, with one or two small filled dots set inside the circle.
Both are built from circles and squares, and both are used in laundry contexts.
Both are built from squares, and both are used in laundry contexts.