Related Clues:

• Pizza slice borders, e.g.
• Minute hands, say
• Shoulder-to-elbow bones
• Half-diameters
• Neighbors of ulnae
• Upper armbones
• Hub-to-rim lines
• Upper arm bones
• Circle lines
• Cuts into a pie, often
• Lines in a circle
• They go straight in a circle
• They're half the diameter
• Shadows on an equatorial sundial, say
• Halves of diameters