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The notation on an engineering drawing, grouped because it is a language rather than a set of pictures: line style carries meaning, symbol position carries meaning, and the same drawing read under the wrong convention comes out mirrored. The projection symbols are the group's most important members — first-angle and third-angle are genuinely incompatible and a drawing must say which it uses. Almost everything here is standardised by bodies whose standards are paywalled, so the records name which standard governs a symbol without pretending to have read it.
A truncated cone shown in two views, stating which projection convention a drawing uses.
A truncated cone in two views, mirrored from the first-angle symbol, stating the American convention.
A long-dash-dot line marking an axis of symmetry or a circle's centre.
A line of short even dashes, showing an edge concealed behind material.
A circle with a diagonal stroke, marking a dimension as a diameter.
A capital R before a dimension, marking it as a radius.
A flat-bottomed bracket shape, calling for a flat-bottomed enlarged hole.
A shallow V shape, calling for a conical widening at a hole's mouth.
A check-mark-like tick with a long arm, carrying surface texture requirements.
An arrow and horizontal reference line carrying weld type, size and process.
A rectangular box divided into cells, stating a geometric characteristic and its tolerance.
A parallelogram, specifying how flat a surface must be.
An upright T on a base line, specifying squareness to a datum.
A boxed letter on a filled or open triangle, establishing a reference.