Final answer:
Indentation curls in skeletal formulas, representing carbon backbones, can start at either end of the zigzag line.
Step-by-step explanation:
In the context of drawing organic molecular structures, indentation curls, also known as zigzag lines in skeletal formulas, can begin at either end of the line. The zigzag lines represent the carbon backbone where each end and bend implies a carbon atom. According to the instructions for drawing skeletal formulas, each carbon atom is assumed to have a total of four bonds, including the bonds shown and the implied hydrogen atoms. In cases where the structure represents cyclical or ring molecules, such as in chair conformations, the orientation of the zigzag begins depending on whether it is the original or the flipped conformation of the molecule.