What is the distinctive shape of the turn-and-slip indicator mark known as?

The turn-and-slip indicator features a distinctive shape known as a "doghouse." This term refers specifically to the design of the indicator's reference symbol, which typically includes a triangular or house-like outline within the gauge. This design allows pilots to easily visualize the orientation of the aircraft during turns, as the movement of the indicator reflects the rate of turn and coordination.

The "doghouse" shape is effective because it provides an intuitive representation of the aircraft's yaw relative to its flight path, helping pilots maintain controlled and coordinated turns. Other shapes like rectangles, pyramids, or circles do not accurately describe this specific instrument and would not convey the same visual information critical for instrument flying.