Square (□) — One Dimension, All Four Sides

The □ symbol before a value states a square shape: the value and its tolerance apply to every side of the feature from one callout — one dimension governing two.

Definition

□10 states a square feature whose every side is 10: the value applies to each of the four sides with the same tolerance. One dimension governs what would otherwise take two — and, the part that matters, the governed sides carry one shared tolerance authority instead of two independent ones.

Why two dimensions are not equivalent

Dimensioning the same feature 10 twice creates two separately toleranced sizes. With a general tolerance of ±0.2, one side could legally measure 10.2 and the adjacent side 9.8 — a rhombus, and both callouts pass. □10 declares one size value for all sides, so the sides stay equal as they vary. Where squareness of the corners must also be bounded, a geometric control takes over from there.

Where it appears

• Square shanks, keys and drive flats where wrench faces must stay equal and parallel
• Square bosses and pockets on cast and machined parts
• Combined with perpendicularity on the sides when the feature must also stand square to a datum
• Rarely on rectangular features — a rectangle needs each dimension stated plainly

What □ does not control

The symbol equalizes the sides; it says nothing about the feature's orientation or location. A perfectly-sized square can sit tilted or misplaced on the part. Orientation to a datum takes a perpendicularity or angularity callout on the square's faces; location takes position — with the size expressed □ so the zone math keeps treating it as one size.