Dimensioning of square features in technical drawing?

There are many ways to dimension square shapes. Whatever way you do it, the shape must have dimensions that show the size of the square, the depth (or height) of the feature, as well as the position.

If it is obvious that the shape is square, a symbol my be used to dimension the size (similar to the way the Ø symbol is used), or "SQ" or "SQUARE" added to the dimension (if following ANSI or ASME standards).

The symbolic means of indicating that a single dimension applies to a square shape shall be to precede that
dimension with the square symbol, as shown in
Figures 6-12 and 6-19. No space is shown between the
symbol and the dimension value.

You can find it into ASME Y14.5-2018 or BS8888