If you draw a shape or a line with the Auto-Stroke option disabled, you’ll see a simple line without any style applied to it. This line will not be visible in the final render, but you can convert this default line into a line with a style applied or a default shape into a shape with a fill using the Create Shape tool (U).
To convert a default line or shape to one with a fill and stroke, simply select the line or shape with the Create Shape tool. The line or shape will turn red when selected, as shown in Figure 13.7. Then press the Spacebar or click the Create Shape button in the Options bar, and the current fill and stroke styles as defined in the Style palette are applied to the selected object.