Final answer:
To sculpt a solid form, two main types of design lines are used: straight lines for structure and stability, and expressive lines for organic, dynamic forms. Historical and modern examples, such as the 'Tulip Chair' and the Laocoon, demonstrate the application of these lines in art and design.
Step-by-step explanation:
The type of design line used to sculpt a solid form is typically a straight line, which provides structure and stability to a composition. This can be seen in architectural elements and classic sculptures where straight lines are oriented to the horizontal, vertical, or diagonal axis of a surface, such as in Michelangelo's David, which exemplifies a sculpture in-the-round with a clear, structured form. However, when it comes to capturing organic, dynamic motion or natural forms in sculpture, expressive lines which are curved, such as the sinuous forms in the Laocoon or the contours of Albrecht Dürer's woodblock print, are used.
In the context of the provided information, the elegant, cylindrical shapes and geometric reliance of the figures, as well as the use of incised lines for details and flat planes, suggest a combination of straight and contour lines to create structure and define shapes, which are evident in historical art examples and modern designs like Eero Saarinen's 'Tulip Chair'.