crow's foot

In manufacturing drawings and technical documentation, a crow's foot is a branching symbol consisting of three short lines radiating outward from a single point, resembling a bird's track. It appears in engineering diagrams to denote that a dimension, feature, or pattern repeats infinitely or continues beyond the shown boundary. The symbol typically sits at the end of a dimension line or extends from an edge to indicate continuation.

The crow's foot serves a specific function in technical communication where space or clarity prevents showing the full extent of a repeating element. On a machined surface specification, a crow's foot at the end of a surface finish symbol means that finish applies to all similar surfaces, not just the one indicated. On a bolt hole pattern, it signals that the pattern repeats in the direction indicated. The symbol eliminates ambiguity and reduces the need for lengthy written notes on drawings.

Use in different contexts

Mechanical drawings use crow's feet most heavily, particularly in aerospace and automotive manufacturing where precision and repeatability are critical. Electrical schematics also employ similar branching symbols, though the formal crow's foot convention appears less frequently there. Pattern makers, tool designers, and CNC programmers encounter these symbols regularly when interpreting drawings for production tooling or checking existing part geometry against specification.

The name derives from the visual resemblance to the three-toed print left by a crow or similar bird. The symbol appears in ISO 128 and similar technical drawing standards, though individual companies may use variations or supplementary notation alongside it. Confusion can arise when the crow's foot is misread as a surface finish callout or when its scope of application is unclear, so proper drafting practice places it precisely relative to the feature it modifies.